Sensor arrangement having thermo-EMF compensation

ABSTRACT

Sensor arrangement providing a signal responsive to a temperature difference between a Hall-effect device output contact and a reference point, having first contact tub located near an external surface of a Hall effect region; second contact tub located near the reference point; first conductor element comprising first and second ends, the first end thermally coupled to the first contact tub and the second end thermally coupled to the second contact tub; second conductor element comprising third and fourth ends, the third end thermally coupled to the first contact tub; third conductor element comprising fifth and sixth ends, the fifth end thermally coupled to the second contact tub, wherein the first and third ends are electrically coupled, the second and fifth ends are electrically coupled, at least two of first, second, and third conductor elements have substantially different Seebeck coefficients, and the signal is tapped at the fourth and sixth ends.

TECHNICAL FIELD

The disclosure relates generally to sensors and more particularly tosensors, systems and methods which compensate for effects of thermalelectromotive force (EMF).

BACKGROUND

Sensors can be affected by many different internal and externalcharacteristics that can make the sensor output signals less accurate.One of these characteristics is thermal electromotive force(thermo-EMF), which relates to the effects temperature can have on themovement of electric charge in a material. A temperature gradient in amaterial, for example, can affect charge flow in the material much likean applied electric field, by pushing charges in a particular direction.This can be amplified in the presence of electric or magnetic fields, orconcentration gradients. Thermal EMFs also can cause temperature-relatedcharges in two primary situations: first, an inhomogeneous temperature(i.e., a temperature gradient) in a homogeneous material, or ahomogeneous temperature in an inhomogeneous material. The second canoccur, e.g., at device contacts, with the voltage referred to as athermal contact voltage. Both are undesirable with respect to sensoroperation and output signal accuracy.

There are many different ways in which temperature can influence charge,only some of which are related to thermal EMF. For example, magneticsensitivity in Hall effect devices and resistivity changes due totemperature generally are not related to any thermal EMF effects andtherefore may not be addressed or compensated for by embodimentsdiscussed herein. Sensor output signals, particularly when the sensorsoperate according to spinning current or voltage schemes, however, canbe affected by thermal EMF. In one example, a sensor system comprisesHall plates which are operated in sequential operating phases. Differentterminals of the Hall plates are tapped as supply and output terminalsin each operating phase, such that the current flow direction or spatialdistribution of current is different from phase to phase. A spinningoutput signal can be obtained by combining the signals from theindividual operating phases. Hall plates, in fact magnetic field sensorsin general, can experience offset errors which result in an outputsignal when there is no applied magnetic field. Offset errors in eachoperating phase can be largely canceled in spinning schemes due to thecombination of the individual operating phase signals, such that littleor no residual offset remains in the combined output signal.

Unfortunately, residual offset errors often remain, such that somespinning scheme sensor systems provide residual offset compensation.Referring to FIG. 1, such systems typically comprise a temperaturesensor arranged in close proximity to the Hall plate because offsetcorrection usually is not constant over temperature. The systemtherefore can sense the temperature, determine a compensation signalbased on the temperature, and take this compensation signal into accountin the spinning output signal. Thus, this conventional approach combinesthe phase temperature signals only by averaging, which can be consideredequivalent to an implicit low-pass filtering of a slow temperaturesensor. A challenge, however, is determining the compensation signal.Because the residual offset of spinning Hall schemes is stochastic, itdepends on the actual individual device, and the temperature of thisdevice, and it can change during the operational lifetime of the device.Thus, even if individual device calibration could be performedefficiently and effectively during end-of-line testing, changes over thelifetime of the device can reduce the accuracy of the calibration andresult in thermal EMF-related residual offset errors.

Conventional solutions presume that thermal EMF effects are canceledthrough use of polarity inversion in sequential operating phases (i.e.,only the polarity of the supply changes) and a spinning voltage ratherthan current technique. This may not be the case, however, because inpractice the temperature distribution can change when the polarity ofthe supply voltage is inverted.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a block diagram of a sensor system.

FIG. 2A is a diagram of a Hall plate according to an embodiment.

FIG. 2B is a diagram of a vertical Hall sensor device according to anembodiment.

FIG. 2C is a diagram of a Hall plate according to an embodiment.

FIG. 2D is a perspective view of a potential distribution in a Hallplate during an operating phase according to an embodiment.

FIG. 2E is a coupling arrangement of a Hall plate in a first operatingphase according to an embodiment.

FIG. 2F is a coupling arrangement of a Hall plate in a second operatingphase according to an embodiment.

FIG. 2G is a coupling arrangement of a Hall plate in a third operatingphase according to an embodiment.

FIG. 2H is a coupling arrangement of a Hall plate in a fourth operatingphase according to an embodiment.

FIG. 2I is a block diagram of a sensor system according to anembodiment.

FIG. 3 is a side cross-sectional view of an arrangement of first andsecond sensor devices according to an embodiment.

FIG. 4A is a diagram of a sensor coupling arrangement according to anembodiment.

FIG. 4B is a diagram of a sensor coupling arrangement according to anembodiment.

FIG. 5A is a block diagram of a sensor system according to anembodiment.

FIG. 5B is a block diagram of a sensor system according to anembodiment.

FIG. 6A is a diagram of another coupling arrangement according to anembodiment.

FIG. 6B is a block diagram of another sensor system according to anembodiment.

FIG. 6C is a block diagram of another sensor system according to anembodiment.

FIG. 7A is a diagram of a coupling arrangement of a Hall plate accordingto an embodiment.

FIG. 7B is a diagram of a coupling arrangement of a Hall plate accordingto an embodiment.

FIG. 7C is a diagram of a coupling arrangement of a Hall plate systemaccording to an embodiment.

FIG. 7D is a diagram of a coupling arrangement of a Hall plate in twooperating phases of a spinning current scheme according to anembodiment.

FIG. 7E is a diagram of a coupling arrangement of a Hall plate in twooperating phases of a spinning current scheme according to anembodiment.

FIG. 8A is a depiction of a temperature distribution in a Hall plateaccording to an embodiment.

FIG. 8B is a depiction of transient temperature behavior of a Hall platein a spinning current scheme according to an embodiment.

FIG. 9 is a side cross-sectional view of an arrangement of a sensordevice according to an embodiment.

FIG. 10 is a diagram of a sensor arrangement according to an embodiment.

FIG. 11 is a diagram of another sensor arrangement according to anembodiment.

FIG. 12 is a diagram of another sensor arrangement according to anembodiment.

FIG. 13 is a diagram of another sensor arrangement according to anembodiment.

FIGS. 14A and 14B are circuit diagrams of a sensor arrangement accordingto an embodiment.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the disclosureto the particular embodiments described. On the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the disclosure as defined by the appendedclaims.

DETAILED DESCRIPTION

Embodiments relate to sensor systems and methods that can compensate forthermal EMF effects that can cause residual offset and other errors insensor systems. In one embodiment, a sensor system comprises at leastone temperature or temperature gradient sensor arranged proximate afirst sensor element configured to sense a physical quantity, such as amagnetic field, temperature, pressure, force, mechanical stress, or someother physical quantity. For example, the first sensor elementcomprises, e.g., a Hall plate in an embodiment in which the sensorsystem comprises a Hall-effect magnetic field sensing system, thoughother types of magnetic field sensors, and sensors more generally, canbe used as the first sensor in other embodiments. In another embodiment,a plurality of temperature sensors can be used, with each one arrangedproximate a different sensor contact or element. In an example in whichthe Hall plate is operated according to a spinning operation scheme, theat least one temperature sensor can be configured to sense a temperaturein each operating phase, and the individual sensed temperatures can becombined and used to provide a temperature-dependent compensationsignal.

Thermal EMF, the characteristic for which embodiments aim to compensate,can be quantified by the Seebeck coefficient for any particularmaterial. For n-doped silicon with a concentration of about10{circumflex over ( )}16/cm³, which is typical for the active region ofHall effect devices discussed herein in some embodiments, the Seebeckcoefficient is about −1,200 μV/° C., at room temperature. N-dopedpoly-silicon with a resistivity of about 7 milli-Ohms*cm has a Seebeckcoefficient of about 200 μV/° C., and n-doped poly-silicon with aresistivity of about 0.8 milli-Ohms*cm has a Seebeck coefficient ofabout 80 μV/° C. Aluminum, often used for metal interconnect lines inintegrated circuit technologies, has a negligible Seebeck coefficient,only about −0.5 μV/° C. These Seebeck coefficients are representativeexamples of materials which could be suitable for use in embodiments,but this list is not exhaustive, nor is it limiting with respect tomaterials which can or may be used, as appreciated by those skilled inthe art. Additionally, the Seebeck coefficient is not critical, andembodiments are related to reducing or eliminating the underlyingthermal EMF.

Embodiments relate to situations in which output signals are tapped atterminals, which can be subject to small additive voltages caused bythermal EMF. In most cases the signals are tapped between two terminalswhich are at different temperatures, and therefore the tapped signal hasa small additive part that is proportional to the temperature differencebetween the terminals. In other cases the signals can be tapped betweena terminal and a reference terminal, such as, e.g., one that is atground potential. Here again the terminal and the reference terminal canhave different temperatures which can cause small superimposed additivethermo-EMF signals. In still other cases a signal can be tapped at thesame contact at different times (e.g., in different operating phases),with multiple sampled values then combined to provide an overall signal.If the temperature at the contact changes over time, a small additivethermo-EMF can be superimposed on the signals. It should be kept in mindthat the different temperatures at the terminals do not affect theisothermal signal (i.e., the signal if the terminals were at identicaltemperatures), so the isothermal signal is not multiplied by some factorthat depends on the temperature difference. Instead, the signal tappedbetween terminals at different temperatures is equal to the isothermalsignal plus a small additive thermo-EMF contribution, which isproportional to the temperature difference between the terminals. It isthis thermo-EMF contribution which embodiments aim to address.

Referring to FIG. 2A, a simplified diagram of a Hall plate 202 isdepicted. The particular depiction in FIG. 2 is not to scale. Thediagram of FIG. 2, as well as others which may be used herein, are forexample and illustrative purposes and are complemented by thisdiscussion, the other figures and this entire application as a whole.Some figures can include block diagrams, wherein the blocks canrepresent physical objects, functions, concepts and/or combinationsthereof. Moreover, while some embodiments discussed herein refer tomagnetic field sensors, including Hall and vertical Hall devices, othersensors can be used in other embodiments, and the use and depiction ofHall plate 202 in this embodiment is not to be considered limiting.

Hall plate 202 comprises three contacts 204 a, 204 b and 204 c. Inembodiments, Hall plate 202 can be operated in a spinning scheme, inwhich contacts 204 a, 204 b, 204 c can be differently coupled as supplyand signal contacts in different operating phases. As previouslymentioned, in a spinning current or voltage scheme, different contactsof Hall plate 202 are coupled in each sequential operating phase suchthat the current flow direction or spatial distribution of current inHall plate 202 is different from one operating phase to the next. Thenumber of contacts and the number of operating phases can vary inembodiments.

While FIG. 2A depicts a single Hall plate 202, in other embodiments, thesensor can comprise a plurality of Hall plates 202 differently coupledwith one another in a similar manner in different operating phases. FIG.2B depicts a cross-section of the Hall device 212 where the top of thedevice 212 is equal to the top of the semiconductorsubstrate—contrarily, FIG. 2A is a plan view onto the main face of asemiconductor substrate. FIG. 2B depicts one example of a vertical Halldevice 212 comprising three contacts 214 a, 214 b and 214 c and whichcan be operated similarly to Hall plate 202 except that vertical Halldevice 212 is sensitive to a different magnetic field component thanHall plate 202, as appreciated by those skilled in the art. FIG. 2C isalso a plan view and depicts an example octagonal Hall plate 202comprising four contacts or contact diffusions 204 a, 204 b, 204 c, 204d. As previously mentioned, the size, shape, configuration and number ofcontacts, among other characteristics, can vary in embodiments, and Hallplate 202 will be used generally herein to refer to a Hall plate withoutlimit with respect to the embodiments of FIGS. 2A, 2C or other Hallplates depicted, vertical Hall device 212 of FIG. 2B, or otherparticular characteristics which can vary from embodiment to embodiment.Hall plate 202 comprises an active region 226 and a boundary orisolation of active region 226 at perimeter 227. FIG. 2D depicts anexample potential distribution within Hall plate 202 in operation. Thedistribution of potential within Hall plate 202 leads to distribution oftemperatures within Hall plate 202, or a spatial distribution oftemperature. The effects of thermal EMF can influence the distributionof potential within Hall plate 202, and therefore also the spatialdistribution of temperature therein.

In one embodiment, at least one temperature sensor can be arrangedproximate Hall plate 202. For example, Hall plate 202 can be arranged ona semiconductor substrate, and a temperature sensor can be arranged inclose physical proximity to one or more contacts 204 a, 204 b, 204 c, toHall plate 202 generally, or another relevant portion of Hall plate 202.In one embodiment, a single temperature sensor is used, and that singletemperature sensor is configured to sense temperatures in Hall plate 202associated with the different power dissipations that can occur in Hallplate 202 in different operating phases of the spinning scheme. Fromthese measurements, system 100 can estimate thermal EMF changes orfluctuations from phase-to-phase. In another embodiment, the temperaturesensor comprises a plurality of temperature sensor elements, for exampleone associated with each contact of Hall plate 202, one positionedbetween each adjacent contact of Hall plate 202, and/or one comprising aplurality of wires or terminals coupled to or with Hall plate 202 suchthat a spatial distribution of temperature in Hall plate 202 can besensed. In essence, however, at least one temperature sensor aims tosense and measure thermal EMF mismatches between different contacts,e.g., two contacts being used in a differential measurement, in Hallplate 202.

The temperature sensor can also be used in embodiments comprising singleoutput voltages or currents, in contrast to differential outputs. Inthese embodiments, the total thermal EMF contributes to the outputsignal at an output contact. One example can be vertical Hall device 212of FIG. 2B, in which current flows between two contacts and an outputsignal is a potential measured at the third contact. Thus, regardless ofwhether the particular sensor implemented is operated in a single phaseor according to a multi-phase spinning current or voltage scheme, thethermal EMF at each output or signal terminal in each operating phase isrelevant to the compensation effort. Vertical Hall device 212 also canbe used in spinning schemes in other embodiments.

The temperature sensor can be sampled during sampling of Hall plate 202in embodiments, such that an instantaneous temperature can be obtained.In one example, operating phases of a sensor device comprising Hallplate 202 are at least about 1 micro-second (μs) long, for example about2 μs, and a temperature sensor that can keep pace and sample signals atappropriate time intervals is needed. In embodiments, therefore, thetemperature sensor is one which has a low thermal mass and heatretention. The temperature sensor also can have a high bandwidth inembodiments. For example, if the Hall sensor 202 is operated in aspinning current scheme at 500 kHz, a suitable bandwidth can be about 1MHz. It is also advantageous in embodiments for the temperature sensorto have a high spatial resolution in order to detect spatial gradientsof temperature in Hall plate 202. In embodiments, the spatial resolutionof the temperature sensor is at least about 10 micrometers (μm), forexample about 1 μm. Additionally, however, the temperature sensor can berelatively simple in embodiments, to avoid adding complexity and expenseto the overall sensor system given that it, and the underlying goal ofthermal EMF compensation, can be an add-on feature in various sensorsystems and implementations. The temperature sensor also should notintroduce or increase parasitic effects, such as high temperatureleakage currents or stray capacitances, particularly those which couldhave an effect on the Hall sensor. Thus, temperature sensors whichrequire too much power, highly sophisticated signal processing, a largearea, or other features which can raise their cost or need for resourceswithin a sensor system can be less suitable in most embodiments butcould still have applicability in certain specialized applications.

Whether the temperature sensor comprises a single temperature sensorelement or a plurality thereof, and whether the temperature sensor isimplemented according to the embodiments of FIG. 3, FIG. 4 or some otherembodiment discussed herein below, the temperature sensor can operate ineach operating phase of a spinning scheme of Hall plate 202 or anothersensor device. In other embodiments, the temperature sensor need notoperate in every phase. The various individual phase temperature signalsfrom the temperature sensor can be combined, while the individual phasesignals from Hall plate 202 also can be combined, by the same ordifferent circuitry, on-chip or off. A temperature signal and a spinningoutput signal can be determined, with the temperature signal used todetermine a temperature-dependent offset correction signal, which can becombined with the spinning output signal to provide an overall systemoutput signal.

For example, and referring to FIG. 2I, a spatial gradient temperaturesensor 230 can be arranged thermally proximate another sensor element232, which can comprise a spinning Hall sensor or some other sensor invarious embodiments, on a substrate 234. Sensor 230 is configured tosense a spatial gradient of temperature within sensor element 232 duringat least a portion of at least one operating phase. For example, sensor232 can be operated in a plurality of operating phases according to aspinning scheme in one embodiment. Circuitry 236, which can be arrangedon or off of substrate 234 in embodiments, is coupled to sensors 230 and232 and can be configured to combine signals of sensor 232 related to asensed physical quantity (e.g., a magnetic field) in each of at leastone operating phases, and to combine signals from sensor 230 related toa sensed spatial gradient of temperature in sensor 232 sampled duringthe same portion of the at least one operating phase. Those signals canthen be combined to obtain an overall output signal indicative of thephysical quantity. Using the combined signals from sensor 230, an offsetcorrection can be determined and used in the combining to obtain theoverall output signal, whereby that overall output signal is correctedfor an offset related to thermal EMF.

Turning to specific example embodiments of a temperature and/or spatialgradient temperature sensor, in one example implementation the sensorcomprises a pn-junction. Pn-junctions are often used to measuretemperature on semiconductor substrates and thus can be suitable invarious embodiments. Pn-junctions also have the advantage of beingrelatively easily arranged in close proximity to the contacts of, e.g,Hall plate 202. One example embodiment of a temperature sensor 104comprising a pn-junction is depicted in FIG. 3. Temperature sensor 104is arranged proximate a Hall plate 202, in particular contact 204 a,spaced apart on a substrate 302 by a distance d with optional galvanicisolation. In other embodiments, temperature sensor 104 and Hall plate202 can be electrically coupled, though this would have an effect on theperformance of one or both of Hall plate 202 and sensor 104 andtherefore may not be suitable in all implementations.

Temperature sensor 104 comprises an n-tub 304 and a p-tub 306, thoughthese can be reversed in other embodiments, and is biased by a constantcurrent source 308. The voltage across current source 308 is a strongfunction of temperature and thus can be used as a temperature sensor.Additional components not specifically depicted, including signalconditioning circuitry components like precision amplifiers andanalog-to-digital converters (ADC) can be included in variousembodiments.

An alternative implementation to that depicted in FIG. 3 is depicted inFIG. 4. Here, temperature sensing is integrated with a Hall or othersensor or type of device by providing additional contacts, terminals,wires, and/or other elements to sense temperatures and/or spatialgradients of temperature in Hall plate 202. The temperature sensing ofthe embodiment of FIG. 4 can be simpler than that of FIG. 3 and candetermine the temperature or a temperature gradient at or withincontacts of Hall plate 202 based on thermal voltage differences betweendifferent materials.

In FIG. 4A, two terminals 204 a and 204 b of a Hall plate 202 (e.g., asdepicted in FIG. 2C or another figure, or having some otherconfiguration whether explicitly depicted or not herein) are shown.Terminals 204 a and 204 b can comprise wires, metal lines or some othersuitable configuration in embodiments. In general, a terminal or a wirecan be a device, circuit or circuit component with a resistance that isless than about ten times a signal output resistance of a sensor deviceat the respective contact which the terminal or wire taps, though thiscan vary in embodiments. It can be advantageous in embodiments to havewires or terminals with a low resistance and low parasitics. Terminals204 a and 204 b, as well as terminals 410 a and 410 b, generally are atthe same temperature T′. Though not depicted in FIG. 4A, terminals 204 aand 240 b can be coupled (e.g., via one or a stack of tungsten plugs) totransistor pairs in a signal amplifier or other circuitry, also arrangedisothermally.

The circuitry and elements of FIG. 4A can be arranged relative to one ormore contacts of a Hall plate or other device, and the Hall plate cancomprise a low-doped n-region in one embodiment, or some otherconfiguration or composition in other embodiments. Terminals 204 a and204 b are each coupled by plugs 402 to an interconnect line 404 a and404 b, respectively, which can be arranged between inter-metal oxidelayers in or on substrate 400. In embodiments, plugs 402 can comprisetungsten-filled holes which have been etched or otherwise formed ininter-metal oxide layers of substrate 400, though other materials,configurations and methods of formation can be used in otherembodiments. Interconnect lines 404 a and 404 b can comprise lines,wires or other suitable structures and couple contacts 204 a and 204 bof the sensor with contact diffusions 406 a and 406 b, respectively, viavarious additional plugs 403 a, 403 b, which can be the same as ordifferent from each other and/or plugs 402 in embodiments. In oneembodiment, contact diffusions 406 a and 406 b comprise shallow n+S/Dcontact diffusions formed in regions 408 a and 408 b. Contact diffusions406 a and 406 b each are coupled to terminals 410 a and 410 b via plugs403 a and 403 b, respectively, and each can comprise an output contactof the sensor for providing a signal related to the physical quantitysensed by the sensor, or a reference point to be used in sensing atemperature difference between two points.

In embodiments, terminals 410 a and 410 b can comprise wires, metallines or other suitable materials or structures. In general, elements204 a, 204 b, 404 a, 404 b, 410 a and 410 b depicted in FIG. 4A each canbe considered to be wires, terminals, interconnects or some otherstructure, including in different contexts given that the figure is apartial representation and merely exemplary, though different terms(e.g., interconnect lines vs. terminals and/or wires) may be used hereinfor purposes of example and illustration. What can be of more interestin embodiments is the Seebeck coefficient of and/or material which thoseelements 204 a, 204 b, 404 a, 404 b, 410 a and 410 b comprise,particularly when considered relative to one another and with respect towhere (i.e., between which terminals and/or wires, and/or betweencontacts) signals are tapped or otherwise considered in variousembodiments.

For example, in embodiments, interconnect lines 404 a and 404 b comprisea different material and/or have a different Seebeck coefficient thanterminals 410 a, 410 b. In one embodiment, interconnect lines 404 a and404 b comprise a semiconductor material, such as polysilicon, silicon,germanium, a single-crystal semiconductor material or a poly-crystallinesemiconductor material, though other materials can be used in otherembodiments, such that the material of interconnect lines 404 a and 404b has a different contact voltage than the material of terminals 410 a,410 b. In another embodiment, the materials can be selected to maximizea difference in Seebeck coefficients therebetween. Thus, there can be adifference in thermal EMF between the materials which can be sensed atterminals 410 a and 410 b, and at terminals 204 a and 204 b, and used tomeasure the thermal EMF. Herein throughout, an example in whichinterconnects 404 a and 404 b comprise polysilicon and terminals 410 aand 410 b comprise a metal generally will be used, though this exampleis not be to limiting with respect to other embodiments. The potentialtherefore can be tapped at the ends of terminals 410 a and 410 b, butalso at terminals 204 a and 204 b, such that the terminals 204 a and 204b can be used to measure a differential signal that can be compared witha differential signal at terminals 410 a and 410 b, which should differfrom one another by the thermal contact voltages between the polysiliconof interconnect lines 404 a and 404 b and the metal of interconnectlines 410 a and 410 b.

In other words, a signal measured between terminals 410 a and 410 b caninclude some unknown thermal EMF contribution caused at least in part bydifferent temperatures T1, T2 of contacts 406 a, 406 b, respectively,and a signal measured between terminals 204 a and 204 b can include thesame unknown thermal EMF contribution in addition to a contribution frompolysilicon interconnect lines 404 a and 404 b. There is a strongcorrelation between the additional polysilicon contribution and theunknown thermal EMF contribution, because they are proportional to thetemperature difference T1−T2 of contacts 406 a and 406 b. Hence, thefollowing can be used:V(C1′)−V(C2′)=F[B]+Off′ and V(C1″)−V(C2″)=F[B]+Off″where F[B] is a function of the magnetic field, with F[0]=0, andOff″=Off′+k(T1−T2), with k being a difference in the Seebeck coefficientof the materials of terminals 410 a and 410 b and interconnect lines 404a and 404 b. C1′ represents terminal 410 a, C2′ represents terminal 410b, C1″ represents terminal 204 a and C2″ represents terminal 204 b inone operating phase, though the coupling arrangements will change fromone operating phase to the next. Referring specifically to FIG. 4:V(204a)−V(204b)=k(404a)*(T1−T′)+k(408)*(T2−T1)+V(408ab)+k(404b)*(T′−T2)V(410a)−V(410b)=k(410a)*(T1−T′)+k(408)*(T2−T1)+V(408ab)+k(410b)*(T′−T2)→V(204a)−V(204b)−(V(410a)−V(410b))==(k(404a)−k(410a))*(T1−T′)+(k(404b)−k(410b))*(T′−T2)An assumption here is that conductive regions 408 a and 408 b have aneffective Seebeck coefficient k(408) and that at isothermal conditions(T1=T2) a voltage V(408 ab) (e.g., an output voltage of a Hall effectdevice) is present between regions 408 a and 408 b tapped at, e.g.,contact diffusions 406 a and 406 b. This assumes that a difference inthe effective Seebeck coefficients between wire or interconnect 404 aand wire or terminal 410 a is the same as the difference in theeffective Seebeck coefficients between interconnect 404 b and wire orterminal 410 b. This can be addressed in embodiments, as discussedherein above, by interconnects 404 a and 404 b comprising the samematerial, and wires or terminals 410 a and 410 b comprising the samematerial. Note that it is the “effective” Seebeck coefficient which isof interest because an individual Seebeck coefficient of one portion ormaterial could be the same. The effective Seebeck coefficients of otherparts or portions of the sensor system are generally irrelevant, so longas the parts or portions are generally at a homogeneous temperature. Forexample, in FIG. 4A the effective Seebeck coefficients of plugs 402comprising tungsten are irrelevant, because there are no spatialtemperature gradients within each of them. Therefore, it makes nodifference if terminal 410 a is coupled to contact diffusion 406 adirectly or via a single tungsten plug or via a stack of two or moretungsten plugs, as long as each tungsten plug has no significanttemperature difference within its body. Thus, in FIG. 4A it would alsobe possible to have a first tungsten plug between contact 406 a and wire404 a and to have a stack of two further tungsten plugs between contact406 a and terminal 410 a such that there is no direct contact betweenthe stack of the two further tungsten plugs and wire 404 a. In practice,a large number of tungsten plugs may be used between contact diffusion406 a and wire 404 a or wire 410 a, all of them electrically connectedin parallel. Since the contact diffusions have finite size, space fortungsten plugs is limited there, and so one is usually inclined to stacklayers, each layer having a large number of parallel connected plugs, asshown in FIG. 4A exemplarily for a single plug per layer. Thus,V(204a)−V(204b)−(V(410a)−V(410b))=(k(404a)−k(410a))*(T1−T2)This enables a measurement of temperature difference T1−T2 if theSeebeck coefficients as mentioned above (e.g., between wire orinterconnect 404 a and wire or terminal 410 a, and between interconnect404 b and wire or terminal 410 b) are different.

The offset of the first sensor (e.g., the Hall effect device) comprisesa raw offset Off and a thermoelectric contribution Off_(therm) accordingto Off′=Off+Off_(therm). The thermoelectric contribution Off_(therm) hasa strong correlation with the temperature difference T1−T2.

While this is valid for a single operating phase, in a spinning schemeHall plate 202 is operated in several phases, and a total signal iscomputed as a sum over all individual phases:S′=Σ(V(C1′)−V(C2′)=Σ(F[B]+Off′)=Σ(F[B]+Off+Off_(therm))measured at terminals 410 a and 410 b, andS″=Σ(V(C1″)−V(C2″)=Σ(F[B]+Off″)=Σ(F[B]+Off+k(T1−T2)+Off_(therm))measured at terminals 204 a and 204 b, with the indices changingaccording to the operating phases. The difference can then be computedby the sensor system:S″−S′=Σk(T1−T2)

Due to the strong correlation, this difference can be used to estimatethe residual offset ΣOff_(therm). One way to obtain this estimation isby a multiplication with a predefined factor x:ΣOff_(therm) ≅xΣk(T1−T2)This factor x can depend on the technology and the geometry of the Hallsensor, as well as on the temperature, operating frequency, electricbiasing and any mechanical stress acting on the sensor. In embodiments,x can be determined based on characterization of sensor devices in thelaboratory or manufacturing-level testing. Once therm is ΣOff_(therm) isdetermined, it can be subtracted from S′ to get a signal without offsetdue to thermo-EMF. Due to spinning Hall schemes, the purely resistiveoffset (i.e., the one which can be described by an asymmetric Wheatstonebridge circuit in an equivalent circuit diagram) vanishes, ΣOff=0, sothat S′−ΣOff_(therm)=S′−x(S″−S′)==(1+x)S′−xS″ is void of any offset.

A simple way, therefore, to measure a temperature difference betweencontact diffusions 406 a and 406 b can be as follows, where T1 is thetemperature at contact diffusion 406 a and T2 is the temperature atcontact diffusion 406 b:T1−T2=(1/k)*(V(204a)−V(204b)−(V(410a)−V(410b)))where k is the difference in the Seebeck coefficients of the metal lines(e.g., terminals 410 a and 410 b) and the polysilicon lines (e.g.,interconnects 404 a and 404 b). This can be efficiently implemented inembodiments because V(410 a)−V(410 b) and V(204 a)−V(204 b) are alreadymeasured by signal conditioning circuitry of the sensor. Dedicatedhardware, such as preamplifiers and ADCs, therefore are not needed tomeasure T1−T2 in embodiments. In another embodiment, T1−T′ can beobtained by determining V(410 a)−V(204 a), and T2−T′ by V(410 b)−V(204b), though dedicated preamplifiers not otherwise needed by the sensorcan be necessary.

Thus, a sensor system can be depicted as system 500 as in FIG. 5A,comprising Hall plate 202. As mentioned elsewhere herein, Hall plate 202of FIG. 5A, or any other figure (e.g., FIG. 6, FIG. 7, etc.) orembodiment whether explicitly depicted or not, can be as depicted in oneof the figures (e.g., FIG. 2A or 2C), having some other configurationnot explicitly depicted, or comprise a vertical Hall device (e.g., Halldevice 212 of FIG. 2B or having some other configuration not explicitlydepicted here). The output signals are tapped at contact diffusions 406a and 406 b by elements (e.g., terminals 204 a, 204 b, 410 a, 410 b andinterconnect lines 404 a and 404 b) forming two different materialpairings which have different Seebeck coefficients as discussed above toobtain a first set of phase signals (e.g., terminals 410 a and 410 b,comprising metal, for example) and a second set of phase signals (e.g.,interconnect lines 404 a and 404 b, comprising semiconductor material,for example, and tapped via terminals 204 a and 204 b). The signals fromall phases are then combined at circuitry blocks 506 and 508, and adifference between the combined signal is determined at block 510. In anembodiment, blocks 506 and 508 can be combined and time-multiplexed,with metal or polysilicon phase signals sampled in any particular phaseand then stored in a memory until combined at block 510. The output ofblock 510 is a measure of temperature asymmetries in the sensor duringthe various operating phases and/or temperature fluctuations of thecontacts (e.g., contacts 204 a, 204 b) during the various operatingphases. It may be equal to S″−S′=Σk(T1−T2). In embodiments, this shouldcorrelate with the residual offset.

This difference, the output of block 510, is then used to estimate theresidual offset at block 512. Its output may be equal to xΣk(T1−T2).This estimated residual offset is then subtracted from the spinningoutput signal from block 508 at block 514 to obtain an overall outputsignal with significantly reduced or removed residual offset, e.g.,according to (1+x)S′−xS″=ΣF[B].

In practice, there are several different ways to implement system 500,which like system 100 of FIG. 1 is a conceptual or generalized depictionof a system and its operation according to an embodiment. In oneembodiment, a first amplifier can be used for the first set of (e.g.,metal) phase signals, and a second amplifier can be used for the secondset of (e.g., polysilicon) phase signals. In another embodiment, thefirst and second sets of phase signals can be multiplexed such that, ina first spinning scheme, the first set of phase signals are amplifiedand processed and, in a second spinning scheme, the second set of phasesignals are amplified by the same amplifier(s). This second embodimentcan be more economical to implement but can be limited by bandwidthrelated to changes in the magnetic field between the first and secondspinning schemes. Nevertheless, at low bandwidths this embodiment can bemore accurate because any amplifier errors are cancelled when the twospinning output signals are combined. Another embodiment of system 500is depicted in FIG. 5B, in which the combined second set of phasesignals (i.e., the output of block 506) is also used to determine theoverall output signal at block 512.

Returning to FIG. 4, FIG. 4B depicts half of the system from FIG. 4Awith a modification of the couplings: instead of connecting both wires404 a, 410 a directly or via tungsten plugs 403 a to the contactdiffusion 406 a of the first sensor device 202, there can also be ashort wire of length d1 between the contact diffusion 406 a and thepoint where both wires are connected together. If d1 is much smallerthan d2, the temperature T11 can be much closer to temperature T1 thanto temperature T′. So the differential input pair of an evaluationcircuit 499 (e.g., a preamplifier in an embodiment) measures a signalproportional to the temperature difference T′−T11, which is close to thetemperature difference T′−T1. It holds that T′−T1=x′*(T′−T11). The samecan be done with the second part of the system labeled with “b” in FIG.4A, such that T′−T2=x′*(T′−T22) holds, whereby T22 is the temperaturewhere wires 410 b and 404 b are shorted. If such a wiring is used inconjunction with FIG. 5A, the output of block 512 would becomexΣk(T1−T2)=xx′Σk(T11−T22). This shows that the change of temperaturedifferences T1−T2 to T11−T22 means only a small modification of thefactor x to xx′ for the offset compensation. If distance d1 is not smallwith respect to d2, this would lead to a notable degradation in themeasurement of temperature differences because (i) these differencesdecrease, and (ii) the thermal influence of other parts of the system onT11, T22 goes up so that finally they are not any more predominantlydetermined by the contact temperatures T1, T2.

In another embodiment, and referring to FIG. 6A, a voltage betweenterminals coupled to a first contact is measured, then a voltage betweenterminals coupled to a second contact is measured. In other words, andreferring to FIG. 6A:V(204a)−V(410a)=k(404a)*(T1−T′)+k(410a)*(T′−T1)V(204b)−V(410b)=k(404b)*(T2−T)+k(410b)*(T′−T2)If the Seebeck coefficients of interconnects 404 a and 404 b are thesame, and the Seebeck coefficients of wires or terminals 410 a and 410 bare the same, then:V(204a)−V(410a)−(V(204b)−V(410b))=k(404)*(T1−T2)+k(410)*(T2−T1)=(k(404)−k(410))*(T1−T2)In FIG. 6A, regions 408 a and 408 b are portions of different tubs, suchas two contacts, one in each of a first and second tub of a Hall device,though in other embodiments regions 408 a and 408 b can be in differentdevices or can comprise part of something other than a tub within one ordifferent devices. A circuit 401 couples two contacts 405 a and 405 b ofregions 408 a and 408 b in embodiments. Then:(204a)−V(204b)=k(404a)*(T1−T′)+k(408a)*(T1′−T1)+V(1′1)+V(2′1′)+V(22′)+k(408b)*(T2−T2′)+k(404b)*(T′−T2)V(410a)−V(410b)=k(410a)*(T1−T′)+k(408a)*(T1′−T1)+V(1′1)+V(2′1′)+V(22′)+k(408b)*(T2−T2′)+k(410b)*(T′−T2)→V(204a)−V(204b)−(V(410a)−V(410b))==(k(404a)−k(410a))*(T1−T′)+(k(404b)−k(410b))*(T′−T2)Thereby a voltage drop across circuit 401 was denoted by V(2′1′) and thevoltage drop between 405 a, 406 a by V(1′1) and the voltage drop between406 b, 405 b by V(22′). For k(404 a)−k(410 a)=k(404 b)−k(410 b), weagain obtain V(204 a)−V(204 b)−(V(410 a)−V(410 b), which is proportionalto (T1−T2), such that the temperature difference can be measured by adifference in signals at terminals 410 a, 410 b and 204 a, 204 b.

Referring also to FIG. 6B, another embodiment of system 500 comprisestwo multiplication factors K1 and K2, which can be chosen in order toimplement the same calculations as those illustrated in and discussedwith respect to FIG. 5B. In a simplified depiction, then, and referringto FIG. 6C, block 508 can carry out one or more of the methodologiesdepicted, at least conceptually, as being separate in FIG. 5A, 5B or 6Bin a single calculation circuitry block 508.

Returning briefly to FIG. 2 and the example Hall devices depictedtherein, FIGS. 2E, 2F, 2G and 2H depict four operating phases of a Hallplate 202 having four contacts 1, 2, 3 and 4. Hall plate 202 has90-degree symmetry and is depicted as a simple square with contacts 1-4arranged at four corners, though this can vary in embodiments. In aspinning voltage scheme having four phases 1-4, supply voltage Vs iscoupled to the contact 1-4 having the same phase number, and the contactopposite that contact is coupled to a ground potential. The tworemaining contacts are shorted such that the output signal is equal tothe current flowing between them. For example, in FIG. 2E, phase 1 isdepicted in which contact 1 is coupled to Vs and contact 3 is coupled toa ground potential. An output signal is measured between contacts 2 and4. The output current therefore can be:I24,1=F1[B]+Off1+k(T2,1−T4,1)+Off1,thermRotating the coupling arrangement of FIG. 2E by one contact in aclockwise direction in the next three phases provides output signals of:I31,2=F2[B]+Off2+k(T3,2−T1,2)+Off2,thermI42,3=F3[B]+Off3+k(T4,3−T2,3)+Off3,thermI13,4=F4[B]+Off4+k(T1,4−T3,4)+Off4,thermThe first element of each equation, e.g., F2[B], represents a magneticfield dependence, which is assumed but need not be different in eachphase. Off1, for example represents a resistive offset term for thefirst phase that can depend on an applied potential and is fully definedby an equivalent circuit diagram, e.g., in the form of an asymmetricWheatstone bridge circuit. The term k(T2,1−T4,1), for example, denotes athermal EMF caused by thermo-coupled contacts, which can comprisealuminum or polysilicon interconnect lines (refer, for example, to FIG.4). The final term, Off1,therm denotes a thermal EMF that occurs insidean active region of Hall plate 202 due to inhomogeneous temperatureand/or inhomogeneous doping gradients.

The sum of the currents tapped at the metal lines (e.g., terminals 410 aand 410 b in FIG. 4), and for which k≈0 is:

$I_{m} = {{\sum\limits_{j = 1}^{4}{F_{j}\lbrack B\rbrack}} + {Off}_{j} + {Off}_{j,{therm}}}$whereas the sum of the currents tapped at the polysilicon lines (e.g.,interconnect lines 404 a and 404 b) is:I _(p) =I _(m) +k(T _(2,1) −T _(4,1) +T _(3,2) −T _(1,2) +T _(4,3) −T_(2,3) +T _(1,4) −T _(3,4))Thus, referring to, e.g., system 500 of FIG. 5A, the following can bedetermined at block 510:I _(p) −I _(m) =k(T _(2,1) −T _(4,1) +T _(3,2) −T _(1,2) +T _(4,3) −T_(2,3) +T _(1,4) −T _(3,4))and it can be used as an input to block 512, which estimates theresidual offset of the spinning voltage Hall plate caused bythermo-voltages

$\sum\limits_{j = 1}^{4}{Off}_{j,{therm}}$because there is a strong correlation between

$\sum\limits_{j = 1}^{4}{Off}_{j,{therm}}$and (T_(2,1)−T_(4,1)+T_(3,2)−T_(1,2)+T_(4,3)−T_(2,3)+T_(1,4)−T_(3,4)),because the latter is the origin of the former. In this example, thecommon mode potential of the output signals is left free but in otherembodiments can be tied to some predefined potential. Thesemethodologies also can be applied to embodiments in which Hall contactsare used as force-sense contacts, in which the voltage or current at aforce-contact is adjusted until the voltage or current, respectively, ata sense-contact is at some predefined value, such as is disclosed inco-owned U.S. patent application Ser. Nos. 13/022,844 and 13/488,709,which are incorporated herein by reference in their entireties. Thesecontacts can be treated in the same ways as the various contactsdiscussed herein such that temperature sensors can be used to measurethe temperature at each sense-contact, or each sense-contact is coupledto the metal lines and polysilicon interconnect lines discussed hereinwith reference to FIG. 4.

These and other embodiments can also comprise additional features,elements, functions and concepts. For example, systems as discussedherein can further comprise heating elements coupled to the contacts ofa sensor to control the temperatures thereof, based on measurements by atemperature sensor, temperature gradient sensor or temperature sensingcircuitry. Additionally or alternatively in various embodiments, aground reference can be adjusted in order to affect the nonlinearcurrent-voltage characteristic of a device and consequently to control atemperature of one or more contacts. Given that the resistance of a Hallelement generally increases as the reverse bias voltage to itssurroundings (e.g., a surrounding tub, substrate, or shallow tub as atop plate) increases, this effect can be used to control the powerdissipation or the spatial distribution of power dissipation and thusthe temperature distribution of the contacts of the Hall plate.Circumferential isolated structures or elements, such as pn-rings ortrenches, also could be used to implement such a feature in variousembodiments. A control loop can be formed in such a way so as to adjustthe power dissipation or the spatial distribution of power dissipationin the Hall plate until the temperature difference signals of thetemperature gradient sensors are minimized. Thereby, the adjustment canbe frozen during a complete spinning cycle or it can be adjusted betweenoperating phases within a complete spinning cycle.

Another embodiment of a Hall plate 202 is depicted in FIG. 7A andcomprises four contacts C1, C2, C3 and C4 and four temperature sensors,which in this embodiment comprise diodes D1, D2, D3 and D4 but cancomprise other devices or structures in other embodiments. ContactsC1-C4 comprise contact diffusions and are labeled in the same order asin FIGS. 2E-2H herein above. In general, the same or similar referencenumerals will be used herein throughout to refer to the same or similarelements, portions, structures or other features in various drawings. InFIG. 7, a top plate of the Hall effect device is optional and notdepicted.

A terminal t1, t2, t3 and t4 is coupled to each contact, i.e., t1 to C1,t2 to C2, t3 to C3, and t4 to C4. A diode D1-D4 is coupled to eachcontact, i.e., D1 to C1, D2 to C2, D3 to C3, and D4 to C4; and atemperature terminal tt1, tt2, tt3 and tt4 is coupled to each diodeD1-D4, i.e., tt1 to D1, tt2 to D2, tt3 to D3, and tt4 to D4. Inembodiments, each diode D1-D4 is arranged in intimate thermal contactwith its respective contact diffusion C1-C4.

As in other embodiments, a spinning current scheme can be implemented,such that in a first operating phase of a spinning current cycle Hallplate 202 is supplied with current at supply contacts C1, C3, and asignal is tapped at signal terminals C2, C4. More precisely, a supplycurrent IsH is injected into terminal t1 and flows into contact C1,while a second terminal t3 is tied to a reference potential VsL, such asa ground potential or some other suitably chosen potential, and a firstoutput voltage is measured across terminals t2 and t4. In oneembodiment, currents IT2 and IT4 are drawn out of terminals tt2 and tt4,such that:|IT2|+|IT4|<|Ish|In embodiments, IsH is about 10 to about 100 times larger than IT2, andIT2 is equal to IT4. If current IT2 flows over diode D2, a voltage dropoccurs over D2. The same is true for diode D4. Therefore, the voltageacross tt4−tt2 is equal to the voltage across t4−t2 plus the differenceof voltages across temperature device D2 and D4:V(t4)−V(t2)=V(t4)−V(tt4)+V(tt4)−V(tt2)+V(tt2)−V(t2)=V(D4)+V(tt4)−V(tt2)−V(D2)Thus:V(tt4)−V(tt2)=V(t4)−V(t2)+V(D2)−V(D4),whereby the voltage V(D2) is considered to be positive if the anode ofdiode D2 is positive with respect to the cathode, and the same appliesto diode D4. According to one embodiment, then, a first temperatureoutput voltage is measured across terminals tt2 and tt4.

The temperature sensors, which are depicted and described as diodes inFIG. 7A but as previously mentioned can vary in other embodiments, arechosen such that the voltage across each is a strong function oftemperature. Because diodes are known to respond by about −2 mV/° C. totemperature changes, they can be suitable in embodiments. In otherembodiments, however, simple resistors, such as those with a largetemperature coefficient of resistivity, can be used. Low-doped tubs arecommon in integrated circuit technology and have temperaturecoefficients on the order of 5000 ppmr C.; for voltage drops of about 1Vacross resistors, then, a temperature signal with a sensitivity of1V*5000 ppmr/° C.=5 mV/° C. may be achieved. A disadvantage of resistorsas temperature devices, however, is their resistance, which adds to theinternal resistance of Hall plate 202 and increases the noise. Diodes,in contrast, have a much smaller internal resistance which does not addmuch noise to the sensor signals. On the other hand, a resistance couldalso be implemented in layers that are above the silicon substrate andthus above the tub of the Hall effect device. For example, apoly-silicon resistor R1, R2, R3 and R4 placed above the respectivecontacts C1-C4 could be used, and an example of such a configuration isdepicted in FIG. 7B. In general, the temperature device also can be anytwo-pole circuit that has a voltage which depends on temperature and, inembodiments, a low internal resistance. In particular, this circuitcould employ feedback loops to reduce the resistance seen by the outputsignal of the Hall effect device.

FIG. 7C depicts a circuit diagram which illustrates one way in which aspinning current Hall probe 202 is connected to preamplifiers A1 and A2in a first operating phase. Switches S1, S2, S3 and S4 are configured toconnect any of the terminals t1-t4 with any of current source IsH,reference voltage source VsL, and/or inputs of amplifier A1.Analogously, switches ST1-ST4 are configured to connect any of terminalstt1-tt4 with any of the inputs of amplifier A2. Current sources IT1-IT4are configured to be switched on or off during arbitrary operatingphases, whereby the shading of IT1 and IT3 is intended to denote thatIT1 and IT3 may be off during the first operating phase (the onedepicted in this figure and in FIG. 7A). Alternatively, all currentsources IT1-IT4 may be on during all operating phases, which mayminimize errors due to transient effects and/or self-heating. Note thatthe sign of the currents IT1-IT4 may be positive or negative, whichmeans that these currents are either drawn out of Hall device 202(positive) or injected into Hall device 202 (negative). This signchanges the common mode potential at the inputs of amplifiers A1, A2 andmay be chosen appropriately. Amplifier A1 subtracts the two outputsignals at t2 and t4 during the first operating phase and provides aphase signal P1 at its output. Amplifier A2 subtracts two temperatureoutput signals at tt2 and tt4 during the first operating phase andprovides a phase temperature signal PT1 at its output. A2 can beidentical to A1 if A1 is operated in a time multiplexed fashion in oneembodiment.

The voltage across a temperature device (e.g., diodes D1-D4) can varylinearly with temperature (at least in a first order approximation):V(D2)=VT20*(1+ST2*T2)V(D4)=VT40*(1+ST4*T4)where T2 and T4 are the temperatures at contacts C2 and C4, ST2 and ST4are temperature sensitivities, and VT20 and VT40 are the voltages acrossD2 and C4 at zero temperature T2 and T4. If the temperature devices areidentical:VT20=VT40 and ST2=ST4.In most cases, however, the temperature devices have a mismatch:VT20< >VT40 and ST2< >ST4Therefore:V(D2)−V(D4)=VT20−VT40+VT20*ST2*T2−VT40*ST4*T4The difference of voltages across both temperature devices is usuallynot zero, even if the temperatures are identical, i.e., T2=T4.

The system can cope with these errors if it executes a third operatingphase in embodiments in which the sources IsH and VsL are swapped. Thus,in this third operating phase, current source IsH is connected toterminal t3 and reference voltage VsL is connected to t1. Thetemperature devices D1-D4 may be still connected the same way as inoperating phase 1. Then:V′(D2)−V′(D4)=VT20−VT40+VT20*ST2T2′−VT40*ST4*T4′where the apostrophe or “'” denotes this operating phase. Note that thetemperatures T2′ and T4′ are different than T2 and T4 because the Halldevice is operated with different current direction and due to smallasymmetries and electrical nonlinearity this can lead to slightlydifferent temperatures (e.g., about 0.01° C. in embodiments). The systemcomputes the difference of differential phase temperature signals asfollows:V(D2)−V(D4)=VT20−VT40+VT20*ST2*T2′−VT40*ST4*T4′and correlates this with the thermoelectric error of the Hall outputsignals during both operating phases:1st operating phase:V(t4)−V(t2)=S*B+k*(T4−T2)3rd operating phase:V′(t4)−V′(t2)=−S*B+k*(T4′−T2′)whereby resistive offset terms are neglected because they are canceledout in the full spinning current cycle. In the overall spinning currentoutput signal both signals of 1st and 3rd phase are subtracted:V(t4)−V(t2)−(V′(t4)−V′(t2))=2*S*B+k*(T4−T4′−T2+T2′)

If the same is done with the phase temperature signals then:V(tt4)−V(tt2)−(V′(tt4)−V′(tt2))=2*S*B+k*(T4−T4′−T2+T2′)+VT20*ST2*(T2−T2′)−VT40*ST4*(T4−T4′)So the phase signals have an error caused by thermo-EMF:k*(T4−T4′−T2+T2′)The phase temperature signals have an extra error caused by thermo-EMF:VT20*ST2*(T2−T2′)−VT40*ST4*(T4−T4′)The system can compare both (e.g. by subtracting them). Thus, the systemcan measure the following:VT20*ST2*(T2−T2′)−VT40*ST4*(T4−T4′)

By characterization in the laboratory it is possible to establish atypical relationship between k*(T4−T4′−T2+T2′) andVT20*ST2*(T2−T2′)−VT40*ST4*(T4−T4′). Such a relationship will vary fromdevice to device, from production lot to lot, but it should be stableover the lifetime of a particular device (i.e., as long as VT20*ST2 andVT40*ST4 are stable, which is generally true in practice if stablepn-junctions or stable resistors or other stable devices are used). Thistypical relationship can be used in an algorithm of the sensor system toestimate the thermo-EMF-error in the phase signals and finally tocompensate for it (e.g. by subtracting the expected error from the phasesignals).

For example, suppose that there is no mismatch between the twotemperature devices D2 and D4. Then the extra error due to thermo-EMF inthe phase temperature signals isV(tt4)−V(tt2)−V′(tt4)+V′(tt2)−V(t4)+V(t2)+V′(t4)−V′(t2)=VT0*ST*(T2−T2′−T4+T4′)where we used VT0=VT20=VT40 and ST=ST2=ST4. If this is multiplied by anappropriate factor and added to the original phase signals in thespinning scheme, the thermo-EMF of the Hall effect device may becanceled:Vcomp=V(t4)−V(t2)−V′(t4)+V′(t2)−x*{V(tt4)−V(tt2)−V′(tt4)+V′(tt2)−V(t4)+V(t2)+V′(t4)−V′(t4)}=2*S*B+k*(T4−T4′−T2+T2′)−x*VT0*ST*(T2−T2′−T4+T4′)=2*S*Bfork+x*VT0*ST=0orx=−k/(VT0*ST)We call Vcomp the thermo-EMF-compensated signal. This factor x can bedetermined empirically, though an approximation can be determinedtheoretically: If a diode is used as a as temperature device, thenVT0*ST=−2 mV/° C.and k is the Seebeck-coefficient of, e.g., a low n-doped Hall regionwith k=−1500 μV/° C. which givesx=−(−1.5 mV/° C.)/(−2 mV/° C.)=−0.75Thus, the thermo-EMF-compensated signal in the first operating phase isobtained by(1+x)*{V(t4)−V(t2)}−x*{V(tt4)−V(tt2)}and in the third operating phase it is given by(1+x)*{V′(t4)−V′(t2)}−x*{V′(tt4)−V′(tt2)}and in the overall spinning scheme both signals are subtracted.

Thus, the thermo-EMF-compensated signal is a linear combination ofdifferential phase signals (e.g., V(t4)−V(t2)) and differential phasetemperature signals (e.g., V(tt4)−V(tt2)), both of the same phase. Inthe above case, the phase temperature signals are weighted with a factorthat is three times larger than the traditional phase signals:−x/(1+x)=−(−0.75)/(1−0.75)=3. Thus, the dominant part of the signalcomes from the phase temperature signals, with only a minor portion fromthe traditional phase signals, a distinction with respect toconventional approaches. Of course, the weight of differential phasetemperature signals versus differential phase signals depends on thetemperature sensitivity of the temperature sensor. As seen above, thelinear combination is independent on the phase: the same factor x ispresent for first and third phases. The devices D2 and D4, however, areassumed to match perfectly. If other devices D1 and D3 are used in thesecond and fourth phases of a spinning Hall cycle, e.g., according toFIGS. 2E-H and they have different VT0 and ST parameters, this will alsoaffect x. So, generally in so-called orthogonal operating phases, i.e.,phases with different signal contacts (phases 1 and 2 are orthogonal,yet 1 and 3 are not orthogonal), the linear combination for thethermo-EMF-compensated signal is different. Yet in non-orthogonal phasessuch as phases obtained by reversing the polarity of the supply voltageor supply current, the linear combination for the thermo-EMF-compensatedsignal is usually identical.

One basic aspect of various embodiments is that the thermal symmetry ofthe Hall effect device with respect to supply reversal can be optimized.If this is achieved for all systematic effects (like, e.g., geometricsymmetry), there will always be some statistical asymmetries (like,e.g., geometric asymmetries due to manufacturing tolerances), whichcause temperature differences between contacts that should haveidentical temperatures without manufacturing tolerances. Thesetemperature differences can be measured by temperature-differencesensors (i.e., sensors of spatial gradient of temperature) and fromthese measurements corrective values are deduced online that canceloffset caused by thermo-EMFs, if these values are added to (notmultiplied with) the Hall effect signal. This feature of adding theoffset-correction value to the uncompensated signal in order to get thecompensated signal can also be seen in the block diagrams in FIGS. 1,2I, 5A, 5B and 6B. This distinguishes embodiments of offset-compensationfrom conventional temperature compensation approaches which multiply anuncompensated Hall signal by some appropriate function of temperature(i.e., a temperature sensor signal) in order to get a compensated signalwith e.g. temperature independent behavior. These conventionaltemperature compensation systems trim the gain of the system as afunction of temperature, whereas embodiments disclosed herein trim theoffset of the system as a function of temperature gradient.

Now, however, suppose that there is a mismatch between two temperaturedevices D2 and D4. The mismatch can occur in VT20< >VT40 or in ST2<>ST4, or in both. We saw above that the subtraction of signals of firstand third operating phases cancels the VT20 and VT40 terms, which isdesired. Since the extra error due to thermo-EMF in the phasetemperature signals is VT20*ST2*(T2−T2′)−VT40*ST4*(T4−T4′), the systemonly has to deal with mismatches between VT20*ST2< >VT40*ST4. Thus, wecan say VT40*ST4=VT20*ST2*(1−MM), where MM is the mismatch between D2and D4. The extra error due to thermo-EMF in the phase temperaturesignals isVT20*ST2*(T2−T2′)−VT20*ST2*(T4−T4′)*(1−MM)=VT20*ST2*(T2−T2′−T4+T4′)+MM*VT20*ST2*(T4T4′)Thus, in the presence of mismatch of temperature devices, the systemdoes not measure T2−T2′−T4+T4′, but rather:T2−T2′−T4+T4′+MM*(T4−T4′)Consequently, the error is moderate as long as T4−T4′ is similar toT2−T2′−T4+T4′. The error is large, however, when|T4−T4′|>>|T2−T2′−T4+T4′|. In other words: The fluctuation oftemperature at an output contact in two operating phases with reversedsupply voltage or current should not be large against the fluctuation oftemperature difference between both output contacts in these operatingphases. This means that the total power dissipation in the Hall effectdevice should change as little as possible when the supply is reversed.It also means that the power density near the output contacts shouldremain as constant as possible when the supply is reversed. Therefore,the operating conditions should be such that the common-mode potentialsat the output contacts should remain identical or nearly so when supplyis reversed in embodiments.

This is illustrated, for example, in FIGS. 7D and 7E. FIG. 7D depicts aHall plate 202 with four contacts C1-C4, which is biased in anundesirable way because the common mode potential (0.5*V(C2)+0.5*V(C4))changes when the supply voltage is reversed due to the electricalnonlinearity of the Hall effect device. The common mode output voltageis slightly below half of the supply voltage due to electricalnonlinearity of the device. Thus, it is about 0.45*V(C1) in the firstoperating phase and 0.45*V′(C3) in the third operating phase. Assuming aperfectly symmetric Hall effect device, then V(C1)=V′(C3), i.e., thesupply voltage is identical if the supply currents are identical butwith different polarities. The common mode output voltages also areidentical in both phases, and consequently the temperature T2 should bevery similar to T2′ (and also T4 should be similar to T4′). Yet if theHall effect device is slightly asymmetrical such that contact C1 is,e.g., about 1% smaller than C3, this will lead to V(C1) being differentfrom V′(C3), and then also the common mode output voltages in bothphases are different. Additionally, the temperatures T2 and T2′ (or T4and T4′) should differ significantly more than before.

FIG. 7E shows the same device biased in a more advantageous way, whereinthe common mode potential is controlled to be at the same level when thesupply is reversed. The operational amplifier OPA compares the referencevoltage Vref with the sum V(C2)+V(C4). If the sum is the larger of thetwo, the output of op-amp OPA goes up, which pulls the gate of the NMOSup such that the NMOS sinks more current, which in turn pulls V(C2) andV(C4) down. Thus the common mode is controlled to a value of Vref/2.

There are numerous other ways to keep the common mode potential at fixedvalues during parts of the spinning Hall scheme, and the examplesdiscussed herein are not limiting. Many of these schemes areadvantageous because they reduce the matching requirements for thetemperature devices, e.g., diodes D2 and D4. A goal, generally, is tokeep the common mode potential of the output constant when the supply isreversed, though the differential potential V(C2)−V(C4) is still free tooutput the magnetic field signal. If the common mode potential isconstant, the power density and thus the temperature distribution alsoshould be constant. Note that the common mode potential can have variouskinds of influences on the Hall region: if the Hall region is isolatedagainst the environment by a reverse biased pn-junction, as is typical,the common mode potential determines the reverse bias and thisdetermines the width of the depletion layer, which defines the activewidth of the Hall region. The thinner the active Hall region, the higherits resistance will be. On the other hand, the common mode potential mayaffect the number of free charges in the active Hall region or at leastin parts of it (e.g., through charge accumulation effects), and thisalso affects the resistance. The resistance also affects the powerdissipation and thus the temperature distribution in the device.

In embodiments, the system estimates T2−T4−T2′+T4′, as was illustratedin the discussion herein above of the simple case with perfect matching.Mismatch will lead to reduced accuracy in this estimation, but a levelof accuracy that is desired or required can vary. In embodiments, thetemperature differences T2−T4 in differential outputs of Hall effectdevices as low as about 0.001° C. can be estimated. This provides athermo-EMF-voltage of about 1.5 μV for a Seebeck coefficient of 1500μV/° C. A typical Hall effect device has a magnetic sensitivity of about50 mV/T when operated at a 1V supply, such that 1.5 μV corresponds to a30 μT offset. This offset occurs at all phases of a spinning Hall probe,and it is stochastic, whereby the offsets in orthogonal phases arepresumably statistically independent and also in the non-orthogonalphases should be basically independent. Thus, if a spinning scheme has 4operating phases, the residual offset should be about sqrt(4), or 2times lower. This gives a residual offset of about 15 μT, whichgenerally corresponds with observations by the inventor in thelaboratory.

When a Hall effect device is operated in a spinning Hall scheme, thetemperature will also vary with each new operating phase. Moreover, thesystem has a certain latency due to the thermal mass of the circuitdevices, and this can lead to the temperature in the n-th operatingphase also being influenced to a certain degree by the temperatureduring the (n−1)-th or, in general, any of the preceding operatingphases. Referring again to FIG. 2E, which shows a Hall effect deviceoperated in a first phase, the contact at highest potential (C1) willalso attain the highest temperature due to the electrical nonlinearityof the device, whereas the grounded contact C3 has the lowesttemperature. If the second operating phase shown in FIG. 2F followsshortly after the first one, contacts C1 and C3 changed roles: in phase1 each was a supply contact, whereas in phase 2 each is now a signalcontact. As C1 was slightly warmer than C3, this gives a temperaturedifference between these two output contacts in the start of phase 2.Consequently, it also provides a thermo-EMF voltage, which causes anoffset error. If phase 2 lasts notably longer than the thermal timeconstant of the Hall effect device, contacts C1 and C3 willeventually—at the end of phase 2—be at identical temperatures, ifperfect symmetry of the device is assumed. Thus, a transient temperaturedifference between the output contacts can occur so that it changesduring a phase, and the duration of the operating phase can have asignificant impact on these effects: if the spinning Hall scheme isexecuted very slowly these transient effects may be ignored, yet, if itis executed very fast the temperature during an operating phase may bepredominantly determined by prior operating phases and only to anegligible extent by the current operating phase. Moreover, the systemmeasures Hall signals and temperature differences synchronously: atevery point in time, when the Hall signal is measured the thermo-EMFerror is part of this Hall signal and therefore the system should knowthe temperature differences at the output contacts for these points intime, too.

Here, however, two types of systems may be distinguished: integratingsystems and sampled systems. An integrating system such as, e.g., acontinuous time sigma-delta analog-to-digital converter (CT-SD-ADC)integrates the Hall output signal during a certain time interval, e.g.,during the entire operating phase. In such a case the system can alsointegrate the temperature-difference between the output contactssynchronously. Alternatively, a successive approximationanalog-to-digital converter (SAR-ADC) usually samples the Hall signal,which means it freezes the value using a sample-and-hold technique andthen converts this static value. In this case also the temperaturedifference of the output contacts can be sampled at the same time theHall signal is sampled.

Under static conditions the temperature distribution in a 100 μm×100μm-square silicon Hall plate with 5 μm thickness and typicalnonlinearity, operated at 3V supply in phase 4 of FIG. 2H, is depictedin FIG. 8A. As can be seen, contact C4 is at highest potential and alsoat highest temperature, about 0.062° C. above a room temperature of 300K.

FIG. 8B depicts the transient temperature behavior of several points inHall plate 202 of FIG. 8A during a spinning Hall cycle. The pulse-shapedcurves denote temperatures of the four contacts, whereas the smoothcurve is the temperature in the center of Hall device 202 (e.g., activearea 226). In this embodiment, each operating phase is about 10 μs long,and there is 300 K initially before the device is powered up. Thus, fastthermal time constants of about 1-2 μs can be seen. Two different pulse“teeth” in each operating phase are also present, which is the high andlow potential supply contacts, and two equal “valleys,” which are theoutput contacts. The temperature difference between supply and signalcontacts is about 0.03° C., whereas the temperature difference betweenboth supply contacts is less than about 0.001° C.

If the initial mismatch between diodes D2-D4 is too large, the systemcan perform an auto-calibration in embodiments. In one embodiment,therefore, a heating element can be used which is designed in such a wayas to generate the same temperature on D2 and D4. This heating elementcan be activated for a certain period of time and then the output ofD2-D4 measured (i.e., either once in an end-of-line calibration, orduring power-up of the sensor system, or repeatedly, e.g., every 100ms). If the output changes when the heating element is activated, thischange is stored and subsequently subtracted from each measurement andused for correction of subsequent measurements.

For example, if the heating element is off, voltages across thetemperature diodes D2-D4 are V(D2), V(D4) and the temperatures at thediodes are T2, T4, respectively. If the heating element is on, thevoltages are V″(D2), V″(D4) with temperatures T2+dT and T4+dT,respectively. The system can measure these voltages and compute(V(D2)−V(D4)−V″(D2)+V″(D4))/(V(D2)−V″(D2)), which is equal to1+VT40*ST4/(VT20*ST2), which gives the mismatch of temperaturesensitivities of both temperature sensors.

Alternatively, some parameter of one or both of diodes D2 or D4 can beadjusted to reduce the observed change in D2-D4-output to zero. Forexample, if D2 and D4 are diodes or resistors, as discussed above, thesystem could change the current IT2 through D2 until the temperaturedifference observed at D2-D4 does not depend on the heating elementbeing on or off. This procedure can trim the sensitivity of D2 to matchD4. Even though the change in IT2 also changes the self-heating of thetemperature sensor, this generally has no adverse effect on the systemas long as this self-heating is the same during on- and off-times of theheater.

Note that usually there are different temperatures at D2 and D4 due tooperation of the Hall effect device or other heat sources present in thesystem. Therefore, the system can extract only the difference intemperature difference between heating element on and off, so only thesuperimposed temperature difference caused by the symmetric heatingelement is relevant. The heating element for auto-calibration should beperfectly symmetric with respect to both temperature sensors D2 and D4(and for orthogonal phases either the same or a different heatingelement needs to be perfectly symmetric to D1 and D3) in embodiments sothat it generates the same temperature increase at D2 and D4 (up tobetter than 1%, such as 0.1% or even better, if possible, inembodiments). There are several approaches which can be used to achievethis: for example, either one heating element is placed symmetricallywith respect to both temperature sensors D2 and D4 (or other diodes ortemperature sensing devices, as the case may be in any particularembodiment or configuration, with the examples here relating thedepiction in the drawings for convenience only), or each temperaturesensor has its own dedicated heating element. In the second case theheating elements should match perfectly, such that now it can be seenthat the problem of mismatch has merely been shifted from D2-D4themselves to their respective heating elements. This still may be aviable option, however, if the mismatch of the heating elements is lessthan the mismatch of the temperature devices. Even in this case it canbe beneficial to make the spacing between temperature sensor andrespective heating element sufficient as every small change in layerthickness or other details may have a large effect on the temperatureexcursion on the temperature sensor caused by the heater.

For example, suppose both D2 and D4 are diodes and have heating elementsHT2 and HT4, which comprise resistive strips placed above them.Resistive strips and this particular placement are but one example ofsuitable heating elements and arrangement. Even if HT2 and HT4 matchperfectly, it is likely that the thickness of an intermetal dielectricor some other structure between HT2 and D2 differs by, e.g., 1% from thesame structure between HT4 and D4. This is all the more likely since thevertical spacing between HT2 and D2 is only about 10 μm or similar.Although HT2 generates the same heat and heat density as HT4, thetemperatures at D2 and D4 would differ. The situation improves, however,if the spacing between D2 and HT2, and also between D4 and HT4, isincreased, e.g., by a lateral distance of about 10 μm. Then the thermalcoupling is less intimate but more stable against production tolerances.On the other hand, the larger the distance between D2 and HT2, thelarger the influence the surrounding area and structures arranged therecan have on the thermal coupling between them. Therefore, it can beadvantageous for the layout of other circuit devices around D2-HT2 andD4-HT4 to be symmetrical in order to have exactly the same thermalcoupling between D2-HT2 and D4-HT4. The same holds if only a singleheating element is used for both D2 and D4; then the mismatch betweenHT2 and HT4 is avoided. Of course, it is typically impractical inpractice to have the layout of the entire system symmetrical withrespect to the heating element and all temperature sensors D1-D4. Thus,in embodiments, it can be made symmetric within a certain distance,whereas at large distances the symmetry can be imperfect so long as thecoupling of the heat source and temperature sensors is still strongenough. With the above given numbers one can estimate if a certainasymmetry is still acceptable: If the mismatch should be reduced toabout 0.1% due to auto-calibration, the thermal coupling between theheating element and D1-D4 must match at least up to about 0.1%. Anyasymmetry can be modelled in a numerical computer code (e.g., a finiteelement simulation) and the thermal coupling can be studied.

If the main sensor has contact diffusions of a first conductivity type(e.g., a Hall sensor has n-doped contact diffusions), then it may bepossible to place smaller diffusion tubs of a second, oppositeconductivity type within the contact diffusions of the firstconductivity type. In the case of the Hall sensor this would be smallerp-tubs within n-tubs. This gives pn-junctions which could be used astemperature device of this respective contact. One example is depictedin FIG. 9, which is a version of FIG. 3 discussed above. Such aconfiguration can save space and make the thermal coupling betweencontacts and temperature sensors more intimate. In an embodiment,contact 204 a can be ring-shaped, completely encircling tub 306 whenviewed from the top (as opposed to the side cross-sectional view of FIG.9) so that the current flowing into/out of the temperature device doesnot affect the potential distribution in the main sensor. Note that FIG.9 is a schematic view of a single contact having an integratedpn-temperature diode; in practice, Hall-effect devices such as Hallplates or vertical Hall-effect devices typically have three or morecontacts each having such a pn-junction. In general, all contacts whichare used to tap a signal in at least one phase of a spinning Hall schemeshould have such a pn-junction.

FIG. 10 is a diagram of a sensor arrangement 1000 according to anembodiment.

By way of overview, the sensor arrangement 1000 overcomes disadvantagesof previous embodiments in that a first conductor element 1020, which iscomposed of a first material having a large Seebeck coefficient andtherefore also a relatively high electrical resistivity (e.g.,polysilicon), is arranged only between two contact tubs 1011, 1012 ofthe Hall device. There the two ends of the first conductor element 1020are electrically coupled to second and third conductor elements 1030,1040, respectively, composed of a second material (e.g., aluminum). Thesecond material has a small Seebeck coefficient and therefore also alower electrical resistivity than the first material, and as a resultthe second and third conductor elements 1030, 1040 may be maderelatively long without their internal resistances becomingimpermissibly high. At the remote ends of the second and third conductorelements 1030, 1040, the voltage is detected and the temperaturedifference between the two contact tubs 1011, 1012 deduced therefrom.

The sensor arrangement 1000 comprises a Hall effect region shown in FIG.10 by the dashed box, contact tubs 1011, 1012, 1013, 1014, a firstconductor element 1020, second conductor element 1030, third conductorelement 1040, supply lines 1050, and signal lines 1060.

The contact tubs comprise first contact tub 1011, second contact tub1012, third contact tub 1013, and fourth contact tub 1014. The firstcontact tub 1011 is located near an external surface of the Hall-effectregion. Optionally, the second contact tub 1012 may be located near anexternal surface of a Hall-effect region. Also, optionally, the secondcontact tub 1012 may be located near the external surface of the sameHall-effect region as the first contact tub 1011. The contact tubs 1011,1012, 1013, 1014 have a large doping concentration. Therefore thecontact tubs 1011, 1012, 1013, 1014 are low ohmic and their Seebeckcoefficient is also relatively small. However, the Seebeck coefficientof the contact tubs 1011, 1012, 1013, 1014, and the Seebeck coefficientof the tungsten plugs, is not relevant as these elements are so smallthat they have a homogeneous temperature. On the other hand, the Halleffect region is relatively large, and there is a temperature gradientbetween the two sense contacts. The Hall effect region may have aSeebeck coefficient of approximately 1.5 mV/degree.

The first conductor element 1020 is shaped as an elongate track andcomprises two ends—a first end portion 1022 and a second end portion1024—located between the first contact tub 1011 and the second contacttub 1012. The first conductor element 1020 comprises, for example,unsilicided n- or p-doped polysilicon, which has a relatively highresistivity, or a shallow p-tub on top of the Hall device, or anymaterial that has a significantly different Seebeck coefficient than themetal of the second and third conductor elements 1030, 1040. Polysiliconhas a Seebeck coefficient of about 200 mV/Kelvin. The first end portion1022 is thermally coupled to the first contact tub 1011. The second endportion 1024 is thermally coupled to the second contact tub 1012. Thetemperature difference between the first and second contact tubs 1011,1012 is to be measured. The ends of the first conductor element 1020 arein contact with the customary aluminum of the wiring plane, such thatfirst and second thermocouples arise at the contact locations.

The second conductor element 1030 comprises two ends—a third end portion1032 and a fourth end portion 1034. The third end portion 1032 isthermally coupled to the first contact tub 1011. The first end portion1022 of the first conductor element 1020 and the third end portion 1032of the second conductor element 1030 are electrically coupled inpunctiform. In practice they are often coupled by one or everal tungstenplugs—if one uses several tungsten plugs then they are usually connectedelectrically in parallel, yet if the metal layer of the 2^(nd) conductorelement is higher than metal 1 it may be necessary to use severaltungsten plugs in series connection, too.

The third conductor element 1040 comprises two ends—a fifth end portion1042 and a sixth end portion 1044. The fifth end portion 1042 isthermally coupled to the second contact tub 1012. The second end portion1024 of the first conductor element 1020 and the fifth end portion 1042of the third conductor element 1040 are electrically coupled inpunctiform.

The second and third conductor elements 1030, 1040 are composed of amaterial (e.g., aluminum or copper) having Seebeck coefficient ofapproximately 1 μV/degree, and have a lower electrical resistivity thanthe first contactor element 1020. The result is the second and thirdconductor elements 1030, 1040 can have relatively long lengths withouttheir internal resistances becoming impermissibly high.

At least two of the first, second, and third conductor elements 1020,1030, 1040 have substantially different Seebeck coefficients, that is,preferably greater than 5 μV/° C., or preferably greater than 15 μV/°C., though the disclosure is not limited in this respect. The differencein Seebeck coefficients may be any difference as considered suitable forthe intended purpose.

The supply lines 1050 are electrically coupled to the third and fourthcontact tubs 1013, 1014. The supply lines 1050 are configured to supplycurrent to the Hall device.

The signal lines 1060 are electrically coupled to the first and secondcontact tubs 1011, 1012. The signal lines 1060 are configured to providean output signal of the Hall device. When there is no magnetic field, itis expected that there would be no output signal of output signalterminals 1062 of the signal lines 1060. However, there is athermocouple where the metal signal lines 1060 contact the n-dopedregions of the contact tubs 1011, 1012 of a different Seebeckcoefficient, resulting in the output signal having a smallthermal-electromagnetic force (EMF), which is related to the temperaturedifference between the first and second contact tubs 1011, 1012. Thefirst conductor element 1020 is electrically coupled with the second andthird conductor elements 1030, 1040, but the conductor elements are notnecessarily electrically coupled with the Hall effect region or any ofthe four contact tubs 1011, 1012, 1013, 1014. Conversely, the supplylines 1050 and the signal lines 1060, 1062 are in electrical contactwith the Hall effect region.

The voltage at the remote ends of the second and third conductorelements 1030, 1040 may be tapped at the fourth and sixth end portions1034, 1044 (i.e., thermocouple signal terminals), and the temperaturedifference between the first contact tub 1011 and the second contact tub1012 deduced therefrom. One of the two remote ends 1034, 1044 or one ofthe 1^(st), 2^(nd), and 3^(rd) conductor elements may optionally becoupled to a reference voltage Vref (not shown). The voltage at thethermocouple signal terminals (fourth and sixth end portions 1034, 1044)is proportional to a temperature difference between third end portion1032 and fifth end portion 1042, that is, the physical contacts betweenthe metal of the second and third conductor elements 1030, 1040 and thepolysilicon of the first conductor element 1020.

During operation, no current flows via the first conductor element 1020and the coupled second and third conductor elements 1030, 1040. Theoutput voltage of the Hall device is measured at the output signalterminals 1062. In addition, the output voltage of the thermocouples ismeasured at the thermocouple terminals (fourth and sixth end portions1034, 1044). These two output voltages can then be combined and acorrelation determined. If one of these voltages is large, the other oneis also large usually. The correlation can be determined, and then themeasured thermocouple voltage can be multiplied by a certain factor andsubtracted from the Hall device output voltage. The result is a Halldevice output voltage corrected for the thermal EMF.

An advantage of the sensor arrangement 1000 over previous sensorarrangements is that the first conductor element 1020 is not as long,and may be, for example, 50 μm. The first conductor element 1020 doesnot run from the sensor arrangement 1000 to a remote amplifier, butinstead runs only between first and second contact tubs 1011, 1012 ofthe sensor arrangement 1000. The result is the internal resistance isnot as large as if the first conductor element 1020 were to run to anamplifier that might be 100-300 μm away, and thus the temperaturemeasurement is more accurate.

FIG. 11 is a diagram of another sensor arrangement 1100 according to anembodiment.

Sensor arrangement 1100 differs from sensor arrangement 1000 of FIG. 10in that the first conductor element, rather than being shaped as anelongate track 1020, is shaped as a round plate 1120 with protrusions(first end portion 1122 and second end portion 1124). The firstconductor element 1120 of this embodiment is wider and thus advantageousin reducing the internal resistance of the temperature measurement.

Sensor arrangement 1100 also differs from the sensor arrangement 1000 ofFIG. 10 in that a signal line of one of the thermocouples is combinedwith a signal line of the Hall device output signal lines. Morespecifically, the third end portion 1032, in addition to beingelectrically coupled to the first end portion 1122, is also electricallycoupled to the first contact tub 1012 at contact 1164. In thisembodiment, the thermocouples are electrically coupled to the Halldevice, such that the common-mode potential of the thermocouples isdetermined by the Hall device. No further reference potential Vref isneeded and a signal line is saved, that is, one of the output signallines having output terminal 1162 is the same as one of the thermocouplelines having fourth end portion 1034.

FIG. 12 is a diagram of another sensor arrangement 1200 according to anembodiment.

Sensor arrangement 1200 differs from sensor arrangement 1100 of FIG. 11in that the first conductor element 1220, rather than being shaped as around plate 1120 is shaped as a square and smaller than the Hall effectregion. Also, the first conductor element 1220, rather than having onlytwo protrusions, has four protrusions.

Sensor arrangement 1200 further differs from sensor arrangement 1100 ofFIG. 11 in that rather than using just two contact tubs (the first andsecond contact tubs 1011, 1012) for thermal-EMF compensation, uses fourcontact tubs 1011, 1012, 1013, 1014. As discussed previously, Halldevices generally operate in a spinning current mode having twooperating phases. In a first operating phase a supply current is sentthrough diametrically opposing contact tubs, and the output voltage ismeasured at the other two contact tubs. In the second operating phasethere is a swap, that is, the first pair of contact tubs is used to tapthe output voltage, and a supply current is sent through the second pairof contact tubs. Since the output voltage is swapped, it is desirable toknow the temperature difference at the contact tubs acting as outputterminals. The contact tubs are swapped every operating phase, so thethermocouples are also swapped. Four thermocouples are therefore needed,with each thermocouple attributed to one of the contact tubs 1011, 1012,1013, 1014.

The first conductor element 1220 comprises four protrusions—first,second, seventh, and eighth end portions 1222, 1224, 1226, 1228—locatedbetween first, second, fourth and third contact tubs 1011, 1012, 1014,1013. The first end portion 1022 is thermally coupled to the firstcontact tub 1011. The second end portion 1024 is thermally coupled tothe second contact tub 1012. The seventh end portion 1226 is thermallycoupled to the fourth contact tub 1014. The eighth end portion 1228 isthermally coupled to the third contact tub 1013. The temperaturedifference between the first and second contact tubs 1011, 1012 is to bemeasured during the first operating phase, and the temperaturedifference between the third and fourth contact tubs 1013, 1014 is to bemeasured during the second operation phase. The ends of the firstconductor element 1020 are in contact with the customary aluminum of thewiring plane, such that respective thermocouples arise at the contactlocations.

A fourth conductor element 1240 comprises two ends—a ninth end portion1242 and a tenth end portion 1244. The seventh end portion 1226 of thefirst conductor element 1220 and the ninth end portion 1232 of thefourth conductor element 1240 are electrically coupled in punctiform, orlike stated above via tungsten plugs.

A fifth conductor element 1230 comprises two ends—an eleventh endportion 1232 and a twelfth end portion 1234. The eleventh end portion1232 is thermally coupled to the third contact tub 1013. The eighth endportion 1228 of the first conductor element 1220 and the eleventh endportion 1244 of the fifth conductor element 1230 are electricallycoupled in punctiform . . . or like above stated via tungsten plugs.

The fourth and third fifth conductor elements 1240, 1230 are similar tothe second and third conductor elements 1230, 1240, in that they arecomposed of a material (e.g. aluminum or copper) with Seebeckcoefficient of approximately 1 μV/degree, and have a lower electricalresistivity than the first contactor element 1220. The result is thefourth and fifth conductor elements 1240, 1230 can have long lengthswithout their internal resistances becoming impermissibly high.

At least two of the first, fourth, and fifth conductor elements 1220,1240, 1230 have substantially different Seebeck coefficients, that is,preferably greater than 15 μV/° C., though the disclosure is not limitedin this respect. The difference in Seebeck coefficients may be anydifference as considered suitable for the intended purpose.

During the first operating phase, the voltage difference signal at theremote ends of the second and third conductor elements 1030, 1040 may betapped at the fourth and sixth end portions 1034, 1044 (i.e.,thermocouple signal terminals), and the temperature difference betweenthe first contact tub 1011 and the second contact tub 1012 deducedtherefrom. The voltage at the thermocouple signal terminals (fourth andsixth end portions 1034, 1044) is proportional to a temperaturedifference between third end portion 1032 and fifth end portion 1044,that is, the physical contacts between the metal of the second and thirdconductor elements 1030, 1040 and the polysilicon of the first conductorelement 1020.

During the second operating phase, the voltage difference signal at theremote ends of the fourth and fifth conductor elements 1240, 1230 may betapped at the tenth and twelfth end portions 1234, 1234 (i.e.,thermocouple signal terminals), and the temperature difference betweenthe third contact tub 1013 and the fourth contact tub 1014 deducedtherefrom. The voltage at the thermocouple signal terminals (tenth andtwelfth end portions 1244, 1234) is proportional to a temperaturedifference between ninth end portion 1232 and eleventh end portion 1232,that is, the physical contacts between the metal of the fourth and fifthconductor elements 1240, 1230 and the polysilicon of the first conductorelement 1220.

During the first operating phase, the sensor arrangement 1200 issupplied with current by lines 1260, and the output signal is tappedfrom lines 1160. During the second operating phase this reverses in thatthe sensor arrangement 1200 is supplied with current by lines 1160, andthe output signal is tapped from lines 1260.

FIG. 13 is a diagram of another sensor arrangement 1300 according to anembodiment.

Sensor arrangement 1300 differs from sensor arrangements 1000, 1100, and1200 of FIGS. 10-12, respectively, in that rather than the thermocouplesbeing in punctiform, they are linear or planar. Thermocouples areintended to detect an average temperature of an entire contact tub, andthus it may be appropriate for the thermocouples to be linear or planar.More specifically, a plurality of contact points between a firstconductor element 1320 and second and third conductor elements 1330,1340 may be arranged along a straight or curved path or over an area, ifthe path or the area is through-connected both to the first conductorelement 1320 and to the second and third conductor element 1330, 1340.If the average temperature of the contact tub 1310 should be detected bythe thermocouple it is advantageous if the contact points between afirst conductor element 1320 and third conductor element encircle thecontact tub to a large degree.

FIG. 13 illustrates a left lower corner of a Hall plate. The dashed lineis a part of the Hall effect region. One contact tub 1310 is shown, butthere are identical contact tubs not shown. The contact tub 1310 haselectrically coupled first contacts 1312.

The first conductor element 1320 may be identical to the top plate of aHall effect device. The top plate is a thin, conductive plate covering asignificant portion of the top surface of the Hall effect region. A mainpurpose of the top plate is to avoid large electric fields acting on therelatively low-doped Hall effect region, because a large electric fieldcould act as a force on mobile ions in the Hall effect region. If theseions move, they change the charge distribution in the Hall effectregion, and this change in charge distribution changes the magneticsensitivity and the offset of the Hall effect device. A top plate iseither a metal or polysilicon plate which is electrically isolated fromthe Hall effect region by some interstitial dielectric layer, and iscoupled to a reference potential, which is usually ground potential.Alternatively, a shallow p-tub may be placed on top of the Hall effectregion, which is an n-tub, whereby the p-tub is coupled to a potentiallower than the lowest potential in the Hall effect device, so that thep-n-junction between top plate and Hall effect region is reverse-biasedand therefore no current flows between them.

This top plate may be the first conductive element 1320, however, thetop plate should be comprised of a material having a Seebeck coefficientthat differs significantly from that of the interconnect layer. Also,the top plate should be coupled with traces of the interconnect layerclose to at least two signal/output contacts.

The top plate of this embodiment is essentially the same size as theHall effect region, but with the exception of rectangular apertures 1324to obtain access to the respective contact tubs. The first conductorelement 1320 has a ring of electrically coupled second contacts 1322distributed on the first contactor element 1320 to surround the contacttub 1310. This ring of second contacts 1342 makes contact with the firstconductor element 1320. The ring of second contacts 1342 measures atemperature of the contact tub 1310. By encircling the contact tub 1310with contacts, it is possible to obtain an average temperature over thecontact tub 1310.

The top plate as first conductor element 1320 may comprise polysiliconand may be electrically isolated from the underlying Hall effect regionby a dielectric layer. Shallow p-doped tubs may alternatively be used asa cover, the tubs being situated in the surface of the n-doped Halleffect region. Such a tub would be advantageous in having a higherSeebeck coefficient, which results in a larger signal with a sametemperature gradient. The layouts or geometries of these covers aresimilar to the embodiments of FIGS. 11-13.

If the first conductor element 1320 is isolated from the Hall effectregion by some interstitial electrically insulating layer, there can beelectrical coupling between the first conductor element 1320 and theHall effect region below. To this end, the insulating layer should beopened, a tungsten plug inserted, and a small contact diffusion added onthe top of the Hall effect region, which is in contact with the tungstenplug. Preferably this contact is in the center of the Hall effect region(in plan view) so that its potential does not increase much during aspinning current scheme. Such a central, fifth contact tub in the centerof the Hall effect region does not cause a large asymmetry and so itdoes not add significant offset error to the Hall effect device. In thiscase the common mode potential of the first conductor element 1320 isequal to the common mode potential of the Hall effect region.Alternatively, the first conductor element 1320 may be electricallycoupled to an interconnect line, and this interconnect line routed to areference potential. In this case the contact tub may also be near thecenter of the Hall effect region, but it may also be anywhere on thefirst conductor element 1320.

The second conductor element 1330 comprises two ends—first end portion1332 and second end portion 1334. The first end portion 1332 iselectrically coupled to the electrically coupled first contacts 1312.The second end portion 1334 is an output signal terminal.

The third conductor element 1340 comprises two ends—third end portion1342 and fourth end portion 1344. The third end portion 1342 iselectrically coupled to the ring of electrically coupled second contacts1342. The fourth end portion 1344 is one thermocouple signal terminalthat may be part of the Hall effect device, and may alternatively be areference point outside of the Hall effect device.

In this embodiment the Hall effect region and the first conductiveelement 1320 are congruent. Contacts between the first conductor element1320 and the second or third elements 1330, 1340 are not at protrusionsas these contacts do not require protrusions.

During operation, the voltage at the remote end of the second conductorelement 1330 at second end portion 1334 may be tapped off in combinationwith the voltage at a corresponding terminal of a second contact tub(not shown) to obtain an output voltage difference between the contacttub 1310 and the second contact tub and a temperature difference deducedtherefrom. The voltage at the remote end of the third conductor element1340 at fourth end portion 1344 may be tapped off in combination withthe voltage at a corresponding terminal of a second contact tub toobtain the output voltage of the Hall device. These two output voltagescan then be combined and a correlation determined. If one of thesevoltages is large, the other one is also large usually. The correlationcan be determined, and then the measured thermocouple voltage can bemultiplied by a certain factor and subtracted from the Hall deviceoutput voltage. The result is a Hall device output voltage corrected forthe thermal EMF.

FIGS. 14A and 14B are circuit diagrams of a sensor arrangement 1400according to an embodiment.

By way of overview, for correcting for thermal-EMF this embodiment uses,instead of a top plate above a Hall-effect device, the Hall-effectdevice itself in a time-staggered manner. In a first operating phase,the Hall-effect device is energized and output signals sampled. In thisfirst operating phase, an inhomogeneous temperature distribution isestablished between the Hall-effect device output contact tubs C1 andC3. Afterward, in a second non-operating phase, the current through theHall-effect device is switched off, such that the voltage distributionin the Hall-effect device is no longer influenced by current flow or amagnetic field. Instead, the voltage distribution is influenced solelyby the Seebeck effect, that is, by thermo-voltages resulting from aninhomogeneous temperature distribution. In other words, in thiscurrent-free state, the thermo-voltages can be tapped off at theHall-effect device output contact tubs C1 and C3, and the temperaturedifference deduced therefrom. However, since the Hall-effect device isnot energized, there is no self-heating, and the temperaturedistribution established in the previously-energized state now decays ata rate determined by the thermal time constants of the sensorarrangement 1400. If the sensor arrangement 1400 can detect thethermo-voltages at the Hall-effect device output contact tubs C1 and C3sufficiently rapidly (e.g., within 1 μsec or less), then thesemeasurement values may be correlated with the temperatureinhomogeneities in the energized first operating state. It is thenpossible to estimate an offset error owing to the temperatureinhomogeneities, and to correct the Hall-effect device output signalwith regard to the offset error.

When the current is switched off during the second non-operating phase,the voltages of the Hall-effect device output contact tubs C1, C3 areinitially floating. One output contact tub C3 is coupled to a referencevoltage by a first voltage source (1.15V). Preferably, this voltage isidentical to the voltage at the output contact tub C3 during the firstoperating phase since the parasitic capacitances at this output contacttub C3 undergoes charge reversal the most rapidly. In the current-freesecond non-operating phase, all other contact tubs C1, C2, C4 thenundergo charge reversal to this voltage with a time constant, whereinthe time constant corresponds approximately to the product of internalresistance of the contact tub and parasitic capacitance at the networknode with respect to ground (e.g., roughly 5 kΩ·200 fF=1 ns). Thecapacitive transients have therefore largely decayed after about 50 nsfollowing switch-off of the supply current, while the thermal transientslast up to 1 μs, or perhaps even 10 μs.

FIG. 14A is a circuit diagram of a sensor arrangement 1400A during thefirst, operating phase.

The sensor arrangement 1400A comprises a Hall-effect device, apreamplifier, switches S1, S2, S3, an NMOS current mirror, a PMOScurrent mirror, a feedback loop, and a first voltage source.

The Hall-effect device comprises contact tubs C1-C4. The contact tubsC1-C4 are configured to energize and to tap an output voltage of theHall-effect device. Contact tubs C1 and C3 are the output terminalswhere the output signal is tapped. The preamplifier is configured toamplify the output signal. The contact tubs C2 and C4 are configured tosupply the Hall-effect device with current.

The PMOS current mirror is a current source, and current is supplied tothe Hall-effect device from this current source via switch SW1.

The feedback loop, which is optional, is configured to draw out currentto control the voltage at switch SW2. The feedback loop comprises anoperational transconductance amplifier (OTA) and a second voltage source(e.g., 0.15V). The OTA is configured to compare the voltages at itsinput terminals. At one input terminal is a reference voltage (secondvoltage source of 0.15V). If the voltage at switch SW2 is higher thanthe reference voltage (0.15V), then the OTA output is high, pulling upthe gates of the NMOS current mirror, which in turn pulls down thevoltage at switch SW2, thereby pulling down the voltage of thenon-inverting input of the OTA. This negative feedback loop is thusconfigured to control the voltage at switch SW2 to be the referencevoltage (0.15V). The switches SW1 and SW2 thus represent supplyterminals.

The voltage at switch SW1 is not controlled directly; it is controlledby the feedback loop. When the first operating phase finishes, and thesecond non-operating phase begins, switches SW1 and SW2 open todiscontinue the current through the Hall-effect device. The Hall-effectdevice still needs to be at some voltage, and that voltage is the firstvoltage via switch SW3, that is, in this case, 1.15V. When the currentthrough the Hall-effect device is switched off, its voltage at theoutput contact tub C3 does not change because it is always coupled byswitch SW3 to the first voltage source of 1.15V. This voltage isnecessary for the preamplifier because the preamplifier is only able tomeasure microvolts; if the voltage changes by 0.5 or 1V, thepreamplifier would go completely into saturation and not function.

The NMOS and PMOS current mirrors may alternatively be replaced by anyother current mirror circuit, such as those comprising bipolartransistors or cascodes. Also, the first and second voltages sources arenot limited to the specific voltage amounts mentioned. These voltagessource may be any voltage amount as suitable for the intended purpose.

In this embodiment there is no dedicated thermocouple because the outputcontact tubs C1 and C3 in the first operating phase are used asconventional Hall-effect signal outputs, and in the second non-operatingphase as thermocouples. In order to use the output contact tubs C1 andC3 as thermocouples, no current can be flowing through the Hall-effectdevice. This is the reason for the two phases.

The first operating phase, as depicted in FIG. 14A, is conventional,with the exception that switch SW3 couples the first voltage source tothe preamplifier. So that this output line from contact tub C3, does notjump in voltage after the current through the Hall-effect device isswitched off, the sensor arrangement 1400 pins this output to the firstvoltage source (1.15V).

FIG. 14B is a circuit diagram of a sensor arrangement 1400B in thesecond, non-operating phase.

In the second, non-operating operating phase directly following thefirst, operating phase, the switches SW1 and SW2 are opened, as shown inFIG. 14B. As a result, current no longer flows into or out of theHall-effect device. However, the voltage at one of the Hall-effectdevice's two output terminals, in this case output terminal C3, is stillmaintained via the first voltage source at 1.15V because the switch SW3is still closed. The Hall-effect device voltage is not free to floatbecause switch SW3 remains closed and keeps the Hall-effect deviceoutput and the preamplifier input tied to the first voltage source(1.15V). At this one preamplifier input there is no change between thefirst and second phases because it is coupled to the first voltage(1.15V). The other preamplifier input is coupled to output contact tubC1 which will now change. In the first operating phase the differencebetween output contact tubs C1 and C3 is caused by the magnetic field ofthe Hall-effect device. But as current no longer flows through theHall-effect device during the second, non-operating phase, the magneticfield no longer has an effect on the output voltage, which nowdecreases. But the thermal-EMF voltage still exists. The output contacttubs C1 and C3 are at slightly different temperatures (e.g., about 20 mKdifferent), and each of these output contact tubs acts as athermocouple. As a result, during the second, non-operating phase, thereis a voltage difference of perhaps 800 μV between the inputs of thepreamplifier.

The preamplifier must measure this thermo-voltage rapidly within a timeperiod that is shorter than the thermal time constant with which thetemperature difference decays. If appropriate, a sample-and-hold elementcan also be used to detect the thermo-voltage shortly after switches SW1and SW2 are opened and to provide the preamplifier with more time forprocessing the voltage.

Small disturbance voltages arise at the Hall-effect output contact tubsC1 and C3 upon switches SW1 and SW2 being opened. The disturbancevoltages are unavoidable since all circuit nodes are loaded withunavoidable stray capacitances. In this regard, after opening switch SW1the connection of the Hall-effect device to switch SW1 falls fromapproximately 2.25V to 1.15V (i.e., −1.1V). At the same time, theconnection of the Hall-effect device to switch SW2 rises from 0.15V to1.15V (i.e., +1V). This asymmetry (−1.1V versus +1.0V) occurs becausethe Hall-effect device has an electrical nonlinearity, such that with avanishing magnetic field the voltage at the output contact tubs C1 andC3 is not exactly in the middle between the supply voltages, but ratheris shifted a little toward the higher voltage. If stray capacitances atboth connections are similar in magnitude (on account of the symmetry ofthe Hall-effect device and similar conductor connections), then negativeand positive charging currents that do not exactly cancel one anotherout must be expected, and the difference leads to a short voltage pulseupon the switching of switches SW1 and SW2. The circuit arrangement 1400should mask out this pulse, for example, by the inputs of thepreamplifier being briefly disconnected from the Hall-effect deviceduring switching.

There are numerous methods to define a common mode potential atpreamplifier inputs in the second, non-operating phase. For example, inthe first operating phase an auxiliary circuit may tap the potentials atcontact tub C3 or C1, or contact tubs C3 and C1, and charge a capacitorto V(C3) or V(C1) or (V(C3)+V(C1))/2. In the second, non-operating phasethe auxiliary circuit no longer charges this capacitor, but insteadcouples the capacitor between ground and any contact tub C1, C2, C3 orC4. Then the potential at contact tub C3 or C1 is defined by thiscapacitor during the entire second, non-operating phase.

An advantage of using the Hall-effect device directly as a thermocoupleis better thermal coupling of the metal/semiconductor junctions (whichconstitute the thermocouples) to the output contact tubs. TheHall-effect device output contact tubs C1 and C3 are measured directlyto obtain real temperatures of the contact tubs, as opposed totemperatures of thermocouples that are close to the contact tubs,resulting in a more accurate temperature measurement. Also, n-dopedcontact tub of Hall-effect device is usually the element with thelargest Seebeck coefficient. This is the worst case for the Hall-effectdevice because it has the largest thermal-induced errors. In the second,non-operating phase the Hall-effect device is used as a thermocouple,but a very sensitive thermocouple. If the top plate is used as athermocouple, then the Seebeck coefficient is 100 or 200 microvolts perKelvin, whereas the Hall-effect device itself has a Seebeck coefficientof around 1,500 microvolts per Kelvin, which is ten times larger. Thisincreases the thermo-offset signal in comparison with the priorembodiments in which the Hall-effect region was not part of thethermocouples.

This embodiment is not merely applicable to traditional Hall-effectdevices. For example, this embodiment is also applicable to mechanicalstress sensor devices, or alternatively vertical Hall-effect devices.The Hall-effect device can usually only measure a magnetic fieldcomponent which is perpendicular to the chip surface, and the verticalHall-effect device can measure in-plane magnetic field componentsparallel to the chip surface. A top plate is electrically isolated fromeach Hall-effect region, for example, by a dielectric isolation layer orby a blocked pn junction, and can be coupled to a voltage by aconnecting line. Such a top plate can be produced from a material havinga Seebeck coefficient having an absolute value greater than that of thealuminum or copper metallization in the semiconductor process. And sucha top plate can be provided with a plurality of connecting lines whichmake contact with the top plate in each case near a contact tub of theHall-effect region, and the temperature at these contact tubs are thusmeasurable.

Thus, various embodiments of sensors, systems and methods forcompensating for the effects of thermal EMF have been discussed herein,with reference to several example embodiments and depictions that arenot limiting to the overall concepts. For example, which examplesrelated to Hall effect sensors have been discussed, other sensor typescan be used, including other magnetic field sensors, mechanical stresssensors, and others. In general, however, the residual offset can becorrelated to temperature fluctuations at sensor contacts, which can inturn be correlated with thermal EMFs, and residual offset can be reducedor eliminated by adding a correction term or compensation signal, or byimplementing a control loop, based on sensed temperatures at one or moresensor contacts.

Various embodiments of systems, devices and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the disclosure. It should be appreciated,moreover, that the various features of the embodiments that have beendescribed may be combined in various ways to produce numerous additionalembodiments. Moreover, while various materials, dimensions, shapes,configurations and locations, etc. have been described for use withdisclosed embodiments, others besides those disclosed may be utilizedwithout exceeding the scope of the disclosure.

Persons of ordinary skill in the relevant arts will recognize that thedisclosure may comprise fewer features than illustrated in anyindividual embodiment described above. The embodiments described hereinare not meant to be an exhaustive presentation of the ways in which thevarious features of the disclosure may be combined. Accordingly, theembodiments are not mutually exclusive combinations of features; rather,the disclosure can comprise a combination of different individualfeatures selected from different individual embodiments, as understoodby persons of ordinary skill in the art. Moreover, elements describedwith respect to one embodiment can be implemented in other embodimentseven when not described in such embodiments unless otherwise noted.Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.Furthermore, it is intended also to include features of a claim in anyother independent claim even if this claim is not directly madedependent to the independent claim.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims for the present disclosure, itis expressly intended that the provisions of 35 U.S.C. Section 112(f)are not to be invoked unless the specific terms “means for” or “stepfor” are recited in a claim.

While the foregoing has been described in conjunction with exemplaryembodiment, it is understood that the term “exemplary” is merely meantas an example, rather than the best or optimal. Accordingly, thedisclosure is intended to cover alternatives, modifications andequivalents, which may be included within the scope of the disclosure.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present disclosure. This disclosure isintended to cover any adaptations or variations of the specificembodiments discussed herein.

What is claimed is:
 1. An arrangement configured to provide a signalresponsive to a temperature difference between a contact of a Halleffect device and a reference point, the arrangement comprising: a Halleffect region; a contact tub located near an external surface of theHall effect region and comprising at least one first contact; a firstconductor element encircling a major portion of the contact tub, andcomprising a plurality of second electrically coupled contactsencircling a major portion of the contact tub, wherein the referencepoint is electrically coupled to the first conductor element, andthermal coupling between the reference point and the contact tub isweaker than thermal coupling between the second electrically coupledcontacts and the contact tub; and a second conductor element comprisingfirst and second end portions, the first end portion electricallycoupled to the plurality of electrically coupled second contacts,wherein the first and second conductor elements have substantiallydifferent Seebeck coefficients, and the reference point and the secondend portion are configured to tap the signal.
 2. The sensor arrangementof claim 1, wherein the substantially different Seebeck coefficients aredifferent by greater than 15 μV/° C.
 3. The arrangement of claim 1,wherein the plurality of second electrically coupled contacts arearranged in a curvature.
 4. The arrangement of claim 1, wherein theplurality of second electrically coupled contacts are arranged in aline.
 5. The arrangement of claim 1, wherein the first conductor elementis identical to a top plate of the Hall effect device.
 6. Thearrangement of claim 5, wherein the top plate comprises a rectangularaperture configured to allow access to the contact tub.
 7. Thearrangement of claim 1, further comprising: a third conductor elementcomprising third and fourth end portions, the third end portionelectrically coupled to the at least one first contact.
 8. Thearrangement of claim 7, wherein the fourth end portion and a secondreference point are configured to tap a second signal.
 9. Thearrangement of claim 8, wherein the signal at the fourth end portion iscombined with a signal at a corresponding end portion of another contacttub to obtain an output signal difference between the contact tub andthe other contact tub.
 10. The arrangement of claim 9, wherein thesignal at the second end portion is combined with a signal at acorresponding end portion of the other contact tub to obtain anotheroutput signal difference between the contact tub and the other contacttub.
 11. The arrangement of claim 10, wherein a correlation isdetermined between the signal and the second signal.
 12. The arrangementof claim 1, wherein the Hall effect region and the first conductorelement are congruent.
 13. The arrangement of claim 1, wherein thecontact tub comprises a plurality of first contacts.
 14. The arrangementof claim 13, wherein the plurality of first contacts are arranged in aline.